EPA-460/3-76-014 

June 1976 

INVESTIGATION 

AND ASSESSMENT 

OF LIGHT-DUTY-VEHICLE 

EVAPORATIVE 

EMISSION SOURCES 

AND CONTROL 

' ·~· . ' ~--· .. ·---~ -~ "~-~-~ ..... ~ ... "-"<--,--.,_~ .... --·---·'"""'~--~--

' ''"". ·~ ...... ~ .. -... ~. -- ,.._~·-·----------_...-_. .... ----""-----

U.S. ENVIRONMENTAL PROTECTION AGENCY 

Office of Air and Waste Management 

Office of Mobile Source Air Pollution Control 

Emission Control Technology Division 

Ann Arbor, Michigan 48105 
This report is issued by the Environmental Protection Agency to report technical 

data of interest to a limited number of readers. Copies are available free of 

charge to Federal employees, current contractors and grantees, and nonprofit 

organizations - as supplies permit - from the Air Pollution Technical Information 

Center, Environmental Protection Agency, Research Triangle Park, North 

Carolina 27711; or, for a fee, from the National Technical Information Service, 

5285 Port Royal Road, Springfield, Virginia 22161. 

This report was furnished to the Environmental Protection Agency by Exxon 

Research and Engineering Company, Linden, New Jersey 07036, in fulfillment 

of Contract No. 68-03-2172. The contents of this.report are reproduced herein 

as received from Exxon Research and Engineering Company. The opinions, 

findings, and conclusions expressed are those of the author and not necessarily 

those of the Environmental Protection Agency. Mention of company or product 

names is not to be considered as an endorsement by the Environmental Protection 

Agency. 

Publication No. EPA-460/3-76-014 

ii 
EPA-460/3-76-014~ 

INVESTIGATION 

AND ASSESSMENT 

OF LIGHT-DUTY-VEHICLE 

EVAPORATIVE 

EMISSION SOURCES 

AND CONTROL 

by 

P . .J. Clark.t• 

Exxon Researt"h and EnJ!;inecrin~ Company 

P.O. Hox 8 

Linden, New Jersey 07036 

Contraet No. 68-03-2172 

EPA Projcet Offin~r: R.E. Kruse 

Pn·pared for 

ENVIRONMENTAL PROTECTION AGENCY 

Off iN· of Air and W astc Mana~emcnt 

Offic·e of Mobile Soun·t• Air Pollution Control 

Emission Control Teehnolo~y Division 

Ann Arhor, MiehiJ?;all 48105 

.lurw IIJ7b 

U.S. Envirohmental Protection Agency 

Region 5, Library (PL -12J) 

77 West Jackson Boulevard, 12th Floor 

Chicago, IL 60604-3590 , 
TABLE OF CONTENTS 

I. INTRODUCTION .. 

I I. SUMMARY . . 

III. EVAPORATIVE CONTROL APPROACHES IN CURRENT USE 

A. 

B. 

Sources of Evaporative Emissions. 

Current Automotive Practice for 

Control of Evaporative Emissions. 

1. Carburetor Evaporative Emission Control 

2. Fuel Tank Evaporative Emission Control. 

3. Charcoal Canisters .. 

4. Purge Systems ... 

5. Summary of Techniques for 

Evaporative Emission Control ..• 

C. Classification of Systems .. 

D. Survey of Evaporative Control Systems 

IV. MAGNITUDE AND SOURCE OF 

EVAPORATIVE EMISSIONS FROM CURRENT VEHICLES 

A. Test Fleet and Test Method .. 

1. Vehicles .... 

2. Vehicle Preparation • 

3. SHED Procedure. 

4. Test Sequence . 

B. Evaporative Emissions from 1973-75 Cars 

1. Total Evaporative Losses from Vehicles. 

2. Background Data . 

3. Evaporative Losses by Mode of Operation 

i 

Page No. 

1 

1 

3 

3 

6 

6 

6 

6 

9 

9 

10 

10 

13 

13 

13 

l3 

16 

17 

17 

17 

20 

20 
v. 

TABLE OF CONTENTS (CONTINUED) 

Page No. 

4. Evaporative Losses by Individual Sources. • . . . 20 

a. Overflow from the 

Carburetor Storage System 

b. Carburetor Leaks. 

c. Overflow from the Charcoal Canister . 

d. Other Losses. 

MODIFICATION OF VEHICLES FOR 

LOWER EVAPORATIVE EMISSIONS • . 

A. Hardware for Better Control 

of Evaporative Emissions. 

1. Air Cleaner Overflow. 

2. Carbon Canister Overflow •. 

3. Carburetor Leaks. 

B. Vehicle Selection and Modification. 

1. Selection .. 

2. Current Emissions 

3. Individual Vehicle Modifications 

for Improved Emission Control 

C. Emissions from Modified Vehicles .. 

1. Evaporative Emissions 

a. Total Evaporative Emissions 

b. Adjustment for Background Levels. 

c. Loss by Mode of Operation •• 

2. Exhaust Emissions . 

D. Conclusions from Vehicle Modification Work 

E. Estimated Costs, Effectiveness 

and Durability of Modifications 

ii 

20 

25 

25 

25 

25 

26 

26 

28 

29 

31 

31 

31 

32 

so 

so 

50 

53 

53 

54 

55 

55 
TABLE OF CONTENTS (CONTINUED) 

VI. EMISSION LEVELS OF MODIFIED VEHICLES 

UNDIO:R SEVERE TEST CONDITIONS. • • • • • 

VI f. 1!1\Ll)CENATED IIYDROCARBONS IN EVAPORATIVE EMISSIONS 

iii 

Page No. 

57 

58 
I. INTRODUCTION 

This report describes a study carried out by the Exxon Research 

and Engineering Company for the EPA to assess the effectiveness of light 

duty vehicle evaporative emission control systems. 

EvaporatLve emissions from light duty vehicles have been controlled nationwide beginning with the 1971 model year vehicle. The 

emissions can be divided into two main categories: (1) carburetor 

emissions, and (2) fuel tank emissions. A control level has been set by 

El'i\ at 2.0 grams per test as measured by the "carbon trap" method. However, an improved measurement technique, the SHED method, has been 

developed recently. (SHED test, Sealed Housing for Evaporative Determinations, is SAE Recommended Practice Jl7la.) The new method has shown 

that the "carbon trap" method underestimates vehicular evaporative emissions. Because of this EPA has sought to conduct a study to determine the 

performance of in-use evaporative control systems with the more accurate 

SHED method. In addition, there is a considerable incentive to improve 

the performance of current evaporative control systems. This is because 

the exhaust hydrocarbon emissions have been reduced considerably in 

recent years and consequently the evaporative hydrocarbons represent 

an appreciable portion of total hydrocarbon emissions of a vehicle. This 

program,undertaken by Exxon Research and Engineering Company,is a study 

which addresses itself to the following facets of the vehicular evaporative 

loss problem: 

1. A survey and analysis of evaporative control systems on 

current vehicles. 

2. A study of the magnitude and source of evaporative emissions from current vehicles using the SHED measurement 

technique. 

3. Modification of vehicles to demonstrate that performance 

of evaporative control systems can be improved. 

4. The effect of severe operating conditions on evaporative 

losses from modified cars. 

II. SUMMARY 

In 1971, evaporative emission controls were imposed by EPA 

on light duty vehicles. This was to limit the loss of hydrocarbons 

evaporating from the fuel tank and carburetor of a vehicle. Recently, 

EPA determined that the test compliance method, known as the "carbon trap" 

method, underestimated evaporative emissions and a new test method has 
- 2 -

been proposed by EPA(l). The new test method, known as the SHED method, 

has shown that the evaporative emission controls in the field are less 

effective than originally estimated and in the case of some critical 

late model vehicles, evaporative emissions are of the same magnitude as 

the exhaust hydrocarbon emission. 

To define and deal with the problem at hand, a program has 

been initiated at Exxon Research and Engineering Company with EPA 

sponsorship. This program has assessed the effectiveness of current 

Evaporative Control Systems (ECS) and has shown the feasibility of 

various hardware approaches which control evaporative emissions to a 

very low level. The performance of ECS's in current use was evaluated 

using a cross section of 1973-75 cars with representative control 

techniques. For this, the Sealed Housing Method for Evaporative 

Determinations (SHED), SAE Jl7la procedure was used. (This involves 

enclosing the vehicles in a shed and monitoring the hydrocarbon level 

in the shed.). The average evaporative loss for a 20 car group was 

8.7 grams/SHED test. The lowest loss was 0.5 gram and the highest was 

30.6 grams. 

The results of this study indicate that the bulk of the 

evaporative losses occur during the hot soak phase of the SHED test, 

and the source of emissions is the carburetor bowl. Current ECS's 

appear effective in handling the diurnal loss from the fuel tank for 

most vehicles. The major source of loss was overflow from the air 

cleanersnorkel, indicating inadequate storage volume for carburetor hot 

soak vapors reaching the air cleaner. Hydrocarbons also escaped from 

poorly fitting seals and other leak sources. In some cases there was 

significant overflow from the carbon canister. 

Hardware was developed to improve ECS performance. Six 

vehicles were modified to demonstrate the feasibility of improving 

current systems. The modifications involved: (1) the venting of the 

carburetor bowl to the canister to alleviate air cleaner overflow, 

(2) utilization of larger carbon beds, (3) adaptation of increased purge 

rates, and (4) sealing and capping of leak sources. These modifications were successful in lowering the evaporative emissions to 

2.0 grams/SHED test or lower for each of the six modified vehicles. 

The costs of the hardware us~d to accomplish this has been estimated 

to vary from $2.00 to $25.00. 

We have concluded from this work that it is feasible to 

markedly improve the performance of current evaporative control systems. 

(1) 41FR2022 
- 3 -

III. EVAPORATIVE CONTROL APPROACHES IN CURRENT USE 

A. Sources of Evaporative Emissions 

The evaporative emissions from a vehicle's fuel system can be 

divided into two main categories, (1) carburetor emissions and (2) fuel 

tank emissions. The evaporative emissions from the carburetor occur 

primarily because of fuel boiling in the carburetor bowl and, to a 

lesser extent, by diffusion across the hydrocarbon concentration gradients 

at the carburetor vents. The first process occurs during the "hot soak" 

period, that is when the heat from the engine is being dissipated to the 

surroundings after shutdown. This causes the temperature of the fuel 

in the carburetor bowl to rise over a period of about 30 minutes during 

which time fuel boils in the carburetor bowl. Beyond this point the 

carburetor slowly cools, the fuel stops boiling and the subsequent losses 

are primarily due to a diffusion process. Most of the carburetor losses 

occur during the rising temperature portion of the soak period. 

The magnitude of carburetor hot soak losses is a function of the 

increase in bowl gasoline temperature during the hot soak, the volume of 

the bowl, and the fuel's volatility. Figure 1 is representative of operation on a gasoline with Reid Vapor Pressure (RVP) of 9 psi (62.1 kPa). 

Typical losses are in the neighborhood of 10-15 grams for a carburetor bowl 

gasoline temperature increase of 10 to 16°C (maximum temperature of 82 to 

88°C). The band in Figure 1 spans the normal size range of carburetor 

bowl volumes from 50 cc (lower curve) to 100 cc. The range of carburetor 

bowl sizes found in the field is much larger than 50-100 cc's, and the 

fuel volatility can vary significantly, thus the range of possible carburetor hot soak losses is much larger. 

Evaporative emissions from the fuel tank are primarily due to 

two concurrent processes which cause an increase in the temperature of 

the fuel in the tank. This rise in tank temperature can occur, (1) while 

the vehicle is standing still due to variation in the ambient temperature 

and the evaporation losses are then referred to as "diurnal losses", (2) 

while the vehicle is operating, due to heat transfer from the exhaust 

system to the fuel tank and the losses are then referred to as "running 

losses". The magnitude of fuel tank diurnal losses is shown in 

Figure 2. The abscissa is the maximum temperature reached during the 

diurnal, normally 27.7°C in evaporative emission testing. Again we are 

using the standard test fuel with a Reid Vapor Pressure of 9 psi (62.1 kPa). 

For the normal range of fuel tank volumes, using the prescribed 40% fuel 

fill, diurnal fuel tank losses vary from 10 to 25 grams or roughly 0.3 gram 

per litre of fuel tank capacity. Diurnal cycles to higher temperatures 

increase evaporative losses as shown. 
FIGL.'Rf 1 

CARBURETOR HOT SOAK EVAPORATIVE EMISSIO~-.s 

ARE STRONGLY AFFECTED BY MAXU1UM BOWL TEMPERATURE DURING SOAK 30 __________ _,_ __ 

25 

20 ~ 

~ 

~ 

z 

c 

~ 

u:. 

u:. 

~ 15 ~ 

5 

ST~~ARD 9 RVP GASOLINE 

65 75 85 

I"IAXD1UH CARBURETOR BOWL TEMPERATURE DURING HOT SOAK, °C 

95 
e 

oc 

.. u:: 

z 

0 

1-1 

u:: 

tJ:l 

50 

40 

~ 30 ~ 

10 

FIGCRE 2 

Dil:L~AL CYCLE EVAPORATIVE ~ISSIO~S 

ARE STRONGLY AFFECTED BY A."!BIE:iT Tu1PERATURE RISE . .'0-""J ITEL :'A ... \"'K VOLU:ffi 

ST~~ARD 9 RVP GASOLI~c 

INITAL GASOLI~~ TEMPER~TGRE, l5.5°c VOU~E 

OF TA11< 

95 Litres 

75 

55 

35 

_j _______________ l __________________________ l ______ . __________ -

20 ?S 30 

MAXI~ DIU~~AL CYCLE TEMPERATURE, °C 
- 6 -

Running losses from most ECS equipped vehicles are not significant. If fuel tanks have non-vented caps and are vented to the intake 

system, the vapors leaving the tank will be burned in the engine. Carburetor bowls are vented to the carburetor air intake, allowing vapors to 

be burned in the engine. 

B. Current Automotive Practice for Control of Evaporative Emissions 

In this section, the types of Evaporative Control Systems (ECS) 

used by the automotive indu~try·are reviewed. 

1. Carburetor Evaporative Emission Control 

The two types of carburetor losses are running losses and hot 

soak losses. The running losses are controlled internally in the carburetor by venting from the carburetor bowl to the air intake of the carburetor via the balance tube (Figures 3 and 4), allowing carburetor running 

vapors to be burned in the engine. This is the case because the pressure 

in the intake is lower than that in the carburetor bowl when the vehicle 

is running. 

To control hot soak losses during engine shutdown, two basic 

systems are used. The first is storage of the vapors in the induction 

system during shutdown followed by eventual consumption in the engine 

after start-up. The hydrocarbon vapors move from the bowl into the 

carburetor intake through the balance tube and then into the carburetor 

throat and air cleaner. Because hydrocarbons are denser than air, they 

displace the air. Figure 3 shows a system of this type. 

The second control system for hot soak losses uses both the 

induction system and a charcoal canister to store vapors. A line from 

the bowl to the canister diverts a portion of the vapors to this alternate storage. This is illustrated in Figure 4. A carburetor vent valve 

opens the line to the canister at idle and while shut down. At other 

times, the line is closed. Vapors stored in the carbon canister are 

ultimately purged by a portion of engine combustion air which is drawn 

through the canister during operating modes. 

2. Fuel Tank Evaporative Emission Control 

Fuel tanks are designed as "closed" systems (non-vented fill 

caps) which are connected to a vapor storage system through a vapor-liquid 

separator. The vapor-liquid separator reduces system load by returning 

condensed and entrained liquid to the tank. Three types of vapor storage 

techniques are used: (1) charcoal canister, (2) engine crankcase, and 

(3) an auxiliary tank. 

3. Charcoal Canisters 

The majority of ECS's use a charcoal canister to store the hydrocarbon vapors emitted from the fuel tank. In most of these systems, the 
- 7 -

FIGURE 3 

EVAl'ORATlVE E~liSSIO:~ CO~TROL SYSTEH 

Carburetor 

Liquid/Vapor 

Separator .----~I 

I' re~;:; ure/Vacuum 

FJ ll.er Gas Cap~ 

Fuel Tank 

Air Cleaner 

Orifice 

+ 

Carburetor 

~~~~~ Bowl 

Tank Vent Line 

Canister---+- 0 0 

0 0 0 0 

0 0 0 0 0 0 

Purge 

Line 

0 ~t0? 0 0 ,//2f~0...,. Filter 

Activated ~l'urg<! Charcoal Air 
- 8 -

FIGURE 4 

EVAPORATIVE EMISSION CONTROL SYSTEM 

Liquid/Vapor 

Separator 

Pressure/Vacuum 

Filler Cap 

Carburetor 

Fuel Tank 

Air Cleaner 

Orifice 

Tank Vent Line 

Canister 

Valve 

Bowl Vent 

- · Line to Bed 

To PCV 

Valve 

Purge 

Valve 

Charcoal Purge Air 
- 9 -

fuel tank vapors from both hot soak and running losses pass into the 

canister. A few systems, however, use a control valve which allows running loss vapors to bypass the charcoal bed and move directly to the engine. 

The charcoal canister system functions via an adsorptionregeneration process. Hydrocarbon vapors are adsorbed on the surface of 

the activated carbon for storage purposes. Later the vapors are desorbed 

from the surface by passing a portion of engine combustion air through 

tht.• charcoal bed. This regeneration, or purging process, is necessary 

to restore the capacity of the bed for further hydrocarbon storage. 

There are several types of carbon canisters in use. They may 

be classified by the method of introducing purge air to the bed and by 

the technique for the handling of running vapors. In most cases, purge 

~ir enters the bed through the open bottom of the canister as illustrated 

in Figure 3. A replaceable filter is used to prevent dust contamination. 

A ~wcond type of canister in use has a sealed bottom with an air inlet 

on top. ln some canisters, running vapors as well as hot soak emissions 

pass into the carbon bed. In others, a purge valve is used which allows 

running vapors to bypass the carbon bed. An example of this type of 

canister is illustrated in Figure 4. 

4. Purge Systems 

There are three general types of purge systems for regeneration 

of carbon beds. These systems can purge to: (1) the air cleaner, (2) the 

carburetor, and (3) the Positive Crankcase Ventilation valve (PCV). Units 

purging to the air cleaner generally utilize the pressure drop through the 

air cleaner and inlet system to draw purge air through the canister. One 

system utilizes the velocity of the air in the air cleaner snorkel to pull 

air through d1e carbon bed. Purging to the carburetor is the most popular 

technique. An example of this is shown in Figure 3. A port at the idle 

position is most often used so that at idle the purge rate will be very 

low but \vill increase as the thrott] e is opened. The third type of purge 

is to the l'CV system. An example of this is shown in Figure 4. With this 

system, a purge valve is used which pennits only tank running vapors to 

reach the engine at idle. As the throttle is opened from idle, engine 

vacuum opens the purge valve on the canister so that both tank running 

vapors and stored vapors in the bed are drawn into the engine via the purge 

air stream. 

5. Summary of Techniques for Evaporative Emission ControJ 

a. Carburetor Bowl 

Emissions 'T'o~ 

~ Induction system only 

~ Both induction system 

and charcoal bed canister 
- 10 -

b. Fuel Tank. 

Emissions To: 

~ Charcoal bed 

- Auxiliary Tank 

~ Engine crankcase 

c. Carbon 

Canister: 

/ Open or closed bottom 

--All vapors enter the bed 

~Running vapors bypass bed 

d, Carbon Canister 

Purges To: 

e. Other 

C. Classification of Systems 

/Air cleaner 

- Carburetor 

~PCV 

Evaporative Control Systems have been divided into two general 

categories: (1) those using a charcoal canister, and (2) those using a 

system other than a charcoal canister for storage of fuel tank vapors. Over 

98% of the 1973-1975 vehicle population utilize a charcoal canister. These 

systems have been further typed according to carburetor storage and type of 

canister purge. This is shown in Figure 5. Systems not using a charcoal 

canister may use the engine crankcase or a small auxiliary tank for storage. 

A further subdivision is by the style of canister. A description of 'the charcoal canisters used by each U.S. manufacturer is given 

in Table I. 

D. Survey of ECS's in Use 

A cross section of about 120 vehicles from the 1973-1975 car 

population has been used in this survey of evaporative control systems 

in current use. In addition to describing the ECS, the fuel system components which affect their function such as proximity of fuel tank to a 

heat source such as muffler, and use of a fuel vapor return line to the 

tank have also been surveyed. This survey covered all families of engines 

from each U.S. manufacturer and the leading foreign-manufactured cars. 

All told, this group is representative of at least 99% of the vehicles 

in the 1973-1975 car population. The results from this survey are shown 

in Appendix I. 
FIGURE 5 

CLASSIFICATION OF EVAPORATIVE D1ISSIO~ CONTROL SYSTENS 

A. Systems Using Charcoal Canisters 

~ Carburetor Storage Type of Canister Purge 

I 

·---- ---- Carburetor 

Induction 

II System PCV 

--- Only 

---- III Air Cleaner 

IV ---- ------ Carburetor 

Induction 1-' 

1-' 

\. System and PCV 

ri ---

Canister 

---- Air Cleaner 

B. Systems l.';'ot Using Charcoal Canisters 

VII ---- Induction ----Tank for Fuel Tank Vapor Storage 

VIII System for Crankcase for Fuel Tank Vapor Storage Carburetor 

IX ---- Vapors ------ Other Than Above 
TABLE I 

CHARCOAL CANISTERS ON U.S. CARS 

Tube Designation 

Manufacturer No. No. of Tubes Inlet Outlet Other Remarks 

General Motors 1 2 Tank Purge 

2 3 Tank Purge 

Carburetor Bowl 

3 3 Tank Purge Vacuum for 

(purge valve) Purge Valve 

4 4 Tank Purge Vacuum for 

(purge valve) Carburetor Bowl Purge Valve 1-' 

N 

Chrysler 1 3 Tank Purge Carburetor Bowl sometimes not used 

Carburetor Bowl 

2 4 Tank Purge Vacuum for 

(purge valve) Carburetor Bowl Purge Valve 

Ford 1 2 Tank Purge 300 gtns 

2 2 Tank Purge 500 gms 

3 3 Tank Purge 700 gms 

Carburetor Bowl 

American Motors 1 2 Tank Purge 

2 3 Tank Purge 

Carburetor Bowl 
- 13 -

JIJ. 11N.;IJ'IIIIJI< /\rJIJ ~;(J(Jf(CJ< IJI' 

l~V_fi_!_'_(~~/\~!J V J·; JoJ1J SSJ0!'4S FHOM CURRENT VEH 1 CLES 

This part of the program evaluated the effectiveness of the 

evaporative control systems in current use on U.S. and imported cars. 

A. Test fleet and Test Method 

1. Vehicles 

The twenty vehicles selected for testing are described in 

Table II. The criteria for their selection were: (1) to be representative of the control techniques in use, (2) to represent carburetor 

designs and fuel tank volumes in the field, and (3) be a cross section 

of the nation's 1973-1975 car population. All vehicles were at l~ast 

90 days old prior to the test date. The source of each vehicle is shown 

in Table III. As far as possible, non-undercoated vehicles were used. 

Prior to completion of the last phase of this program, it was necessary 

to return Car No. 3 and replace it with Car No. 21 which was similar in 

make, model and engine to its predecessor. 

2. Vehicle Preparation 

Each vehicle underwent a mechanical inspection and was tuned 

to factory specifications in cases where the ignition system and 

exhaust emissions were abnormal. For this, the ignition system was 

checked by an electronic analyzer and the exhaust emissions by the 

diagnostic procedure(l) developed by Exxon Research for tail pipe CO and 

HC emissions at idle and 2500 rpm. 

Other preparation involved thermocouple installations in the 

carburetor bowl, the underhood area, and the fuel tank. The thermocouple 

for underhood temperatures was located about four inches in front of the 

carburetor bowl. In addition to the in-tank thermocouple required by 

the SAE Jl7la test method, a skin type was attached to the outside of the 

tank at the fuel-air interface. A new fuel tank was used for each vehicle. 

1wo lines were welded into the tank, a drain line and a line from the vapor 

space in top of the tank. This latter line is for a transducer connection 

to monitor fuel tank pressure during the diurnal and hot soak cycles. The 

integrity of the fuel tank system was checked prior to the initiation of the 

test. 

(1) J. Panzer, "Idle Emissions Testing - Part II," SAE Paper 740133 
TABLE II 

VEHICLES FOR SHED TESTS 

(All Automatic TransMission Except 1119) 

Car DisEl· No. 

No. Make Model Yr. Lit res ---

Cu. In. _3_L_-

1 Ford LTD 75 5.75 351 8 

2 Pontiac G.P. 75 6.56 400 8 

3 Chrysler NYer 75 7.21 '•40 8 

4 Ford Pinto 74 2.00 122 4 

5 Chevrolet Nova 74 4.10 250 6 

6 Chevrolet Impala 74 5.74 350 8 

7 Plymouth Duster 73 3.69 225 6 

8 Buick Le Sabre 75 5.74 350 8 

9 Chevrolet Vega 75 2.29 140 4 

10 Oldsmobile 98 74 7.46 455 8 

11 AMC Hornet 74 3.80 232 6 

12 Plymouth Fury III 73 5.90 360 8 

13 Dodge Dart 74 5.21 318 8 

14 Datsun 610 74 1. 95 119 4 

15 Hazda RX-4 74 1.31 80 Rotary 

J6 Mercury Cornet 74 4.10 250 6 

17 Volvo 144 74 1.98 121 4 

1'3 Ford Squire 75 7.54 l!60 8 

19 vw Beetle 75 1.60 97 4 

20 Mercury Monarch 75 '•· 95 302 8 

(1) Type of Evaporative Control System (ECS) described in Fi8ure 5. 

(2) Canister has a purge control valve. 

(3) Also uses a carbon canister for fuel tank vapor storage. 

(4) Fuel injection. 

(5) Carbon canister for fuel tank vapor storage. 

(6) Condensor tank for fuel tank vapor storage. 

No. Fuel Tank 

Venturis Litres Gals. -·----

2 92 24 

4 95 25 

l: 100 26.5 

2 49 13 

1 79 21 

2 93 26 

1 60 16 

4 98 26 

2 60 16 {! 93 26 

1 6b 17 

2 98 26 

2 60 16 

2 52 14 

4 64 17 

1 60 l(j 

F. I. (4) 60 16 

!I 79 21 

F.r.(4) t,o 10.5 

2 73 19 

Air Vapor Return ECS(l) 

C0nd. Line? ------

Undercoated ~ 

y tT N VI 

y y N I 

y y y IV 

IJ ~: ~~ III 

y N N II (2) 

y }! y I 

y ;r y IV 

y y y I ,, }.' y v(2) ·' 

y y y I 1-' 

y N y III .1:-

y }) y IV 

y N y I 

y y y VIII 

y y y VII (3) 

y N N III 

N y N IX (5) 

y y y VI 

N y N IX (6) 

y v y Il'I 
Car No. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

- 15 -

TABLE III 

SOURCE OF VEHICLES 

Hake 

LTD 

Pontiac 

Chrysler 

Pinto 

Nova 

Chevrolet 

Duster 

Buick 

Vega 

Olds 

Hornet 

Plymouth 

Dart 

Datsun 

Hazda 

Comet 

Volvo 

Ford 

vw 

Monarch 

Chrysler 

Source 

Leased 

Leased 

Leased 

Leased 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

Private Owner 

ERE Car 

Private Owner 

Private Owner 

Private OT11ner 

Leased 

Leased 

Private Owner 
- 16 -

3. SHED Procedure 

Evaporative losses were measured using the Sealed Housing for 

Evaporative Determinations (SHED) procedure as described in SAE Recommended 

Practice Jl7la. This method employs an enclosure in which the vehicle is 

placed during diurnal and hot soak phases of the test. Vapors escaping 

from the vehicle are retained in the enclosure and the increase in the 

hydrocarbon concentration of the atmosphere in the enclosure represents 

the evaporative emissions. 

Details for the SHED test are outlined in SAE Jl7la. These 

were followed in this work with one or two exceptions such as for 

preconditioning. Some of the operational steps for the test are covered 

below: 

Preconditioning: 

The preconditioning procedure for this test was as follows: 

(1) three consecutive LA-4(1) cycles [7.5 mile (12.1 krn) trips), 

(2) shut down for 10 minutes, and (3) a fourth LA-4 cycle. This was 

followed by an 11-16 hour soak at about 24°C. 

Diurnal Cycle: 

A one hour soak in the SHED during which the temperature of 

the fuel in the tank is raised from 60 to 84°~ (15.6 to 28.9°C). A 

pressure transducer was used to monitor fuel tank pressure during the 

diurnal cycle and the hot soak. 

Federal Test Cycle: 

The vehicle was quickly placed on the chassis dynamometer after 

the diurnal cycle for an exhaust Federal Test Procedure. The dynamometer 

had previously been warmed up with a different vehicle and the load set. 

Hot Soak: 

A one hour hot soak in the shed followed immediately after the 

Federal cycle to complete the test. 

The fuel for the SHED test was Indolene of 9.0 psi (62.1 kPa) 

RVP. Inspections for this fuel are shown in Appendix II. 

(1) 1972 Federal Test Procedure 
- 17 -

4. Test Sequence 

The sequence of testing for each vehicle is outlined in the 

diagram in Figure 6. Those vehicles which emitted less than 2 grams/ 

test were tested a second time by the SHED procedure to complete their 

test cycle. All vehicles failing the 2 gram limit underwent a source 

test to determine the location of the leaks. This was followed by two 

tests to quantify the emissions from individual leak sources using the 

technique described in Appendix III. A third quantifying test was made 

in cases where there was an abnormal variance between the first two 

tests. This was followed by a second SHED test to complete the testing 

Hchedule. (Hot and cold background tests were also carried out on each 

vehicle as per SAE Jl7la.) 

B. Evaporative Emissions from 1973-75 Cars 

1. Total Evaporative Losses from Vehicles 

Total losses, as measured by the SHED procedure, varied from 

a low 0.5 gram to a high of 30.6 grams for the 20 car group. The average 

for the group was 8.7 grams. The range for the 20 cars is shown graphically 

below: 

20 

Grams 15 

Per 

Test 

10 

5 

0 

,.~ 

~ 

f1-

-

-

1-

~ 

I I 

TOTAL EVAPORATIVE LOSSES 

20 Cars 

Vehicles 

....!:.""' 

-

-

-

-

-

-
- 18 -

FIGURE 6 

FLOW DIAGRAM OF TESTING PROCEDURE 

( START ) 

-

BACKGROUND 

TESTS 

SHED 

TEST 

0 IF SHED 

Em. ~ 2 Gr. TEST 

IF 

Em. > 2 Gr. ~ 

SOURCE - IF j 

LOCATION TEST Em. > 2 Gr. \ 

INDIVIDUAL 

SOURCE TEST(l) 

IF , Em. :;;: 2 Gr. 

INDIVIDUAL 

SOURCE TEST(Z) 

(1) :/: 

IF 

(2) 0 

IF (1) = (2) 

INDIVIDUAL ~ SHED 

SOURCE TEST()) TEST 

( END 

~ \_ 

J 

-
- 19 -

In tllis program, the data arr· for tlH• most part an ;lv•·r;l)'.'' ul 

two SilEO tests. The initial test may be slightly higher than the HPcond 

SHEU test because leaks in the air cleaner were sealed prior to the 

second test (as part of the quantifying procedure). In cases where 

there was a substantial difference between the two SHED tests, a third 

was run and the three averaged for the vehicle. The total evaporative 

loss was adjusted for vehicle background hydrocarbon levels. The 

results for individual runs on each car are summarized in Appendix IV. 

The table below shows total evaporative losses by make and 

model in descending order from worst to best. No particular U.S. manufacturer appears to stand out from a good performance standpoint. A 

Plymouth Duster was the best U.S. car, however, the Chrysler NYer is 

one of the poorest for high evaporative losses. Some models from both 

G.M. and Ford also are comparatively good and others fall in the poor 

category. The best vehicle was a fuel injected VW Beetle with only 0.5 

gram total evaporative loss. The other fuel injected vehicle in the 

group, the Volvo, falls in the poorest half of the 20 car group. 

Table IV 

Total Evaporative Losses By Make and Model 

Total Loss Car ECz 

Grams Make Model Yr. No. Type l) 

30.6 Ford Country Squire 75 18 VI 

17.3 Mercury Comet 74 16 III 

17.1 Chrysler NYer 75 3 IV 

10.9 Chevrolet Nova 74 5 II 

10.7 AMC Hornet 74 11 III 

10.6 Mazda RX-4 74 15 VII 

9.5 Olds 98 74 10 I 

9.3 Mercury Monarch 75 20 Ill 

7.5 Volvo 144 74 17 IX 

7.5 Pontiac G.P. 75 2 I 

6.7 Ford LTD 75 1 VI 

6.6 Buick Le Sabre 75 8 I 

6.0 Ford Pinto 74 4 III 

5.8 Plymouth Fury III 73 12 IV 

5.3 Chevrolet Impala 74 6 I 

4.1 Chevrolet Vega 75 9 v 

2.8 Dodge Dart 74 13 I 

2.8 Datsun 610 74 14 VIII 

1.5 Plymouth Duster 73 7 IV 

0.5 vw Beetle 75 19 IX 

(1) -ECS type described in Figure 5. 
- 20 -

No single type of ECS system appears to be superior to the 

others in the above table. There are, however, desirable features from 

individual ECS ~ystems which will be discussed later. 

2. Background Data 

Evaporative losses from sources other than the fuel system are 

generally small. Cold background data for U.S. vehicles fall in the 

range of 0.0 to 0.2 grams per test. Hot backgrounds were higher ranging 

for 0.0 to 0.7 grams per test. Table V and Appendix IV show individual 

vehicle background data. The only car to have a high background from a 

non-fuel oriented source was the 1975 VW, Car No. 19. The background 

levels of this vehicle were 0.7 and 0.8 grams cold and hot respectively. 

These do not appear to be the result of gasoline absorption from previous 

spillage on the vehicle as was the case for several test cars. Both the 

hot and the cold background tests were continued for 24 hours. The rate 

of hydrocarbon .emission did not diminish significantly during the 24 hour 

periods. Comprehensive probing for the source of hydrocarbon emission 

did not reveal any sources. Additional testing showed that essentially 

all of the hydrocarbon was coming from the outside of the vehicle and only 

a small fraction from the interior. This vehicle is at least 5-6 months 

old. It appears that the paint may be the source of the emission. 

3. Evaporative Losses by Mode of Operation (Test Cycle) 

The bulk of the evaporative losses occur during the hot soak 

mode of operation. Evaporative losses by mode of operation are shown in 

Table VI. For the U.S. cars in this group, 83% of the evaporative loss 

was experienced during the hot soak. This means that most U.S. cars 

handle fuel tank vapors from the diurnal cycle satisfactorily in their 

carbon canister storage system. The loss during the diurnal cycle for 

70% of the U.S. cars was 10% or less of the total loss. For the remaining U.S. cars, diurnal losses were as high as 65% of the total loss. 

Imported vehicles follow the same pattern as the U.S. car population. 

4. Evaporative Losses by Individual Sources 

a. Overflow from the Carburetor Storage System 

Hydrocarbon vapors escaping from the air cleaner during the 

hot soak are by far the largest contributor to evaporative losses. One 

half of the hydrocarbon loss is by this route with vapors escaping from 

the air cleaner snorkel. This indicates that the air cleaner and induction system do not have sufficient capacity to store all of the vapors 

emitted from the carburetor bowl during shut down. A summary of the contribution from each source to the total emission for the cars is shown in 

Table VII along with the mode of operation during which the loss occurs. 

The source of losses for individual vehicles is summarized in Table VIII. 
- 21 -

TABLE V 

EVAPORATIVE LOSSES ADJUSTED FOR BACKGROUND 

Total Loss Before Total Loss 

Car Background Adjustment, Background, Grams Adjusted for 

No. Grams Cold Hot Background, Grams ------------ ----

1 6.7 __ (1) __ (1) 6.7 

2 7.5 __ (1) __ (1) 7.5 

3 17.2 0.0 0.1 17.1 

4 6.2 o.o 0.2 6.0 

5 11.0 0.0 0.1 10.9 

6 5.3 __ (1) --(1) 5.3 

7 1.5 __ (1) -- (1) 1.5 

8 7.0 0.1 0.3 6.6 

9 4.7 0.0 0.6 4.1 

10 10.0 0.2 0.3 9.5 

11 10.8 0.0 0.1 10.7 

12 6.6 0.1 0.7 5.8 

13 2.9 0.0 0.1 2.8 

14 3.1 0.1 0. 2 ( ) 2.8 

15 12.2 o.s(2) 1.1 2 10.6 

16 17.4 0.0 0.1 17.3 

17 7.7 0.1 0.1 7.5 

18 30.7 0.0 0.1 30.6 

19 2.0 0. 7 (3) o.s<3) 0.5 

20 9.3 0.0 0.0 9.3 

~No background data for these cars. The results from the background 

tests for Cars No. 1, 2, 6 and 7, which were the first four to be 

tested for background, were very high due to gasoline spillage on 

the front carpet. A fuel can had been used as an auxiliary fuel tank. 

This took place after the SHED testing. Procedure changed after these 

four cars. 

(2) Evidence of gasoline spillage in the trunk prior to the SHED tests, 

which would account for the high background. 

(3) Appears to be coming from external enamel paint. 
- 22 -

TABLE VI 

EVAPORATIVE LOSS BY MODE OF OPERATION 

Total Loss, % of Loss 

Car No. Grams Diurnal Cycle Hot Soak 

1 6.7 50 50 

2 7.5 5 95 

3 17.1 45 55 

4 6.0 30 70 

5 10.9 2 98 

6 5.3 10 90 

7 1.5 

8 6.6 10 90 

9 4.1 5 95 

10 9.5 5 95 

11 10.7 5 95 

12 5.8 65 35 

13 2.8 5 95 

14 2.8 35 65 

15 10.6 0 100 

16 17.3 0 100 

17 7.5 60 40 

18 30.6 5 95 

19 0.5 

20 9.3 20 80 
Location 

1 - Air Cleaner(l) 

- 23 -

TABLE VII 

SUMMARY OF SOURCES OF EVAPORATIVE 

LOSSES FROM 20 CAR GROUP 

Mode 

Hot Soak 

2 - Carburetor Leaks(2) Hot Soak 

3 - Carbon Canister Diurnal 

4 - Carbon Canister Hot Soak 

5 - Other Diurnal & H.S. 

(1) Snorkel - other leaks sealed before tests. 

% of 

Total Losses 

50 

25 

10 

10 

5 

(2) Primarily from around accelerator pump shaft. Some smaller leaks 

elsewhere. 
- 24 -

TABLE VIII 

SOURCES OF EVAPORATIVE LOSSES 

% of Total EvaEorative Loss 

Air Cleaner Carbon Canister 

Car Total Loss, Diurnal Hot Diurnal Hot Carb. 

No. Grams Cycle Soak Cycle Soak Leakage SHED(l) 

---

1 6.7 0.0 0.0 45 45 0.0 10 

2 7.5 0.0 60 5 5 25 5 

3 17.1 0.0 2o<2> 45( 2) 20(2) 10 5 

4 6.0 0.0 65 30 0.0 0.0 5 

5 10.9 0.0 45 0.0 0.0 5oO> 5 

6 5.3 0.0 95 0.0 o.o 0.0 5 

7 1.5 

8 6.6 o.o 70 0.0 0.0 25 5 

9 4.1 o.o 90 0.0 0.0 0.0 10 

10 9.5 o.o 75 0.0 0.0 20 5 

11 10.7 o.o 40 0.0 0.0 60 0.0 

12 5.8 0.0 0.0 35 35 30 0.0 

13 2.8 0.0 60 0.0 o.o 35 5 

14 2.8 ls(2) 0.0 45 4o(5) 

15 10.6 0.0 100 0.0 0.0 

16 17.3 0.0 85 0.0 0.0 15 0.0 

17 7.5 5 50 0.0 0.0 35 (4) 10 

18 30.6 0.0 20 0.0 10 65 5 

19 0.5 

20 9.3 o.o 25 20 o.o 50 5 

(1) Hydrocarbon vapors not collected in quantifying test or otherwise accounted for. 

(2) Estimated. 

(3) This carburetor also externally vented upon slight pressure in bowl. 

(4) Leakage from gas cap. 

(5) Crankcase storage. 
- 25 -

The vehicles with the lowest loss from the air cleaner were 

those utilizing both canister and air cleaner storage for vapors from 

the carburetor bowl. These are Type IV-VI systems. Using the canister 

to handle part of the hot soak load alleviates the overloading of the 

air cleaner. However, unless the canister has sufficient working capacity to adsorb the added load, it in turn will overflow. 

b. Carburetor Leaks 

This is the second largest contributor to evaporative losses 

and accounts for 25% of the total loss. For the most part, these leaks 

occur 1n carburetors which do not utilize a diaphragm type of accelerator 

pump (used in Ford Motor Company and some other carburetors). Sixty 

percent of the cars tested had problems with hydrocarbon leakage around 

the accelerator pump shaft where it passes through the air horn or body 

of the carburetor. Car No. 5, in addition to leakage around the accelerator pump linkages, vented to the atmosphere with a slight pressure 

buildup in the carburetor bowl. 

c. Overflow from the Charcoal Canister 

This is the third largest source of evaporative emissions with 

10% occurring during the diurnal cycle and an additional 10% during the 

hot soak. This indicates insufficient working capacity in the canister 

of five of the twenty cars in the group. Vehicles with overflow during 

the hot soak utilized the carbon bed to store carburetor bowl vapors as 

well as fuel tank vapors. 

d. Other Losses 

Some hydrocarbon is lost from small leaks such as from the 

ends of the throttle shaft as it passes through the carburetor body and 

other places. Running losses during the Federal Cycle were not measured. 

The most likely source of running vapors is venting through the gas cap 

due to pressure build-up in the tank. Car No. 17 was the only vehicle to 

have a significant pressure build-up in the fuel tank. It vented hydrocarbon vapors through the gas cap during the diurnal cycle and hot soak 

and probably during the Federal Cycle. 

V. MODIFICATION OF VEHICLES FOR LOWER EVAPORATIVE EMISSIONS 

The purpose of this phase of the program is to develop hardware 

to give better control of emissions, select vehicles with typical or 

representative sources of evaporative emissions, and then to modify the 

vehicles to demonstrate the effectiveness of the new hardware. 
- 26 -

A. Hardware for Better Control of Evaporative Emissions 

1. Air Cleaner Overflow 

Five techniques to control air cleaner overflow during the 

hot soak are shown as Controls No. 1 through 5 in Table IX and discussed 

below: 

Control No. 1 - Vent the Carburetor Bowl to the Canister 

A portion of the hot soak emissions is directed to the carbon 

canister for storage in lieu of the air cleaner. A valve in the carburetor 

opens to vent the bowl to the canister during idle and shutdown. At other 

times, the vent line is closed. Venting of the bowl to the canister is now 

used in the ECS's of Vehicles No. 1, 3, 9, and 12. This modification 

requires minimum flow resistance in the line to the canister, viz. lin~ 

should slope toward the canister and be of adequate size to handle the 

vapor load. Undue resistance to flow results in excessive hydrocarbon 

vapors entering the air cleaner via the carburetor bowl balance tubes. 

This modification requires a larger storage capacity in the carbon canister 

than ECS's with air cleaner storage only for hot soak emissions. The 

canister must now accommodate both the hot soak and the diurnal emissions 

at the same time. 

Control No. 2 - Ventilating Engine Compartment with a Fan 

A fan is used to provide cool air to the engine compartment to lower 

the temperature increase of the bowl during the hot soak. The lower bowl 

temperature contributes to a decrease in hot soak emissions and lessens the 

load on the storage system. The fan can be actuated by a thermal switch 

through the ignition system. This will cool the engine compartment until 

its temperature is lowered to the control point at which time the fan is 

shut off. 

Control No. 3 - Barrier at the Base of the Air Cleaner Snorkel 

Hydrocarbon vapors are heavier than air and tend to preferentially 

settle down. A barrier at the base of the snorkel deters the loss of emissions out the snorkel. 

Other controls to limit air cleaner overflow such as decreasing 

carburetor bowl volume and use of louvers in the hood for ventilation are 

suggested in Table IX. They were not included in this program. 
Control 

No. 

1* 

2* 

3* 

4 

5 

6* 

7* 

8* 

9* 

10 

11 

12* 

13 

14* 

15 

Source 

Air cleaner overflow 

Air cleaner overflow 

Air cleaner overflow 

Air cleaner overflow 

Air cleaner overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Canister overflow 

Carburetor leaks 

Carburetor leaks 

TABLE IX 

~1ETHODS FOR CO~ITROL OF EVAPORATIVE E1ISSIONS 

Description 

Vent carburetor bowl to canister. 

Ventilating engine compartment with a 

fan during hot soak. 

Barrier at base of snorkel. 

Decrease bowl working volume. 

Louvers in hood for ventilation. 

Increase size of carbon bed. 

Increase purge rate. 

Close bottom of canister and vent to 

top of unit. 

Control ~o. 2 

Controls No. 4 and 5 

Heat purge air. 

Minimize heat input to fuel tank. 

Shield tank from hot muffler, etc. 

Minimize vapor space in the fuel tank. 

Close spaces around shafts with boots, 

caps, etc. 

Use a diaphragm type accelerator pump 

in lieu of the plunger type. 

*Controls demonstrated in this program. 

Remarks 

Less vapors generated because of lower 

carburetor bowl temperatures. 

Less vapors generated. 

Less vapors generated. 

Two canisters used in parallel. 

Apply for ECS with carburetor bowls 

vented to the canister. 

For ECS's with vented bowls to the 

canister. 

Less vapors generated. 
- 28 -

2. Carbon Canister Overflow 

Eight techniques are suggested for control of an overloaded 

carbon canister. These are shown as Control 6 through 13 on Table IX 

and described below: 

Control No. 6 - Increase Size of Carbon Bed 

This modification will increase the working capacity of the system. 

(Working capacity is the maximum weight of hydrocarbon that can be handled 

in the storage unit.) In many cases, it is not necessary to increase 

purge rate to realize an increase in working capacity with a larger canister. 

This is the casebecause, even though the purge flow rate is lower per unit 

of charcoal with a larger bed, the average hydrocarbon loading on the 

charcoal during the purge cycle is higher, resulting in more hydrocarbon 

being removed from the canister. 

Control No. 7 - Increase the Purge Rate 

This technique will increase the working capacity of those canister 

storage units which currently have low purge rates. ECS's which utilize 

air cleaner purge systems, Type III and VI, generally have low purge volumes. 

In many instances, it may be necessary to utilize carburetor or PCV purge 

systems to raise the purge volume to the desired level. 

Control No. 8 - Close the Bottom of Open Canisters 

This would prevent seepage or migration of hydrocarbon from the 

bottom of the open canister. A sketch of a cover with a vent pipe is shown 

on the following page. 
- 29 -

CAP PREVENTS LOSS FROM BOTTOM OF CANISTER 

Inlet Purge Air 

G.M. Canister --

Cap for Open Bottom 

Controls No. 10 through 13 in Table IX outline additional 

controls to handle canister overflow. These controls were not used in 

this program with exception of Control No. 12 which was applied to 

Vehicle No. 17. 

3. Carburetor Leaks 

Two controls are suggested for carburetor leaks as indicated 

below: 

Control 14 - Use of Flexible Boot and Covers 

Carburetor leaks around accelerator pump shafts can be 

prevented by use of a flexible boot around the shaft to seal the opening. 

In cases where a boot will not suffice, a cover such as the one shown in 

Figure 7 can be used. 
- 30 -

FIGURE NO. 7 

SKETCH OF A SEAL FOR CARTER CARB. LEAK. - CAR NO. 11 

I --- ·--r ... ~~~-=~~~ 

Accel. Pump Shaft ------ I I 

I 

Carb. Body 

Carb. Base 

Throttle Shaft 

and Linkage 

Cover Design: The two sides and bottom would be cast into the carburetor base. 

Front side would be held in place with a snap clip. 
- 31 -

Control 15 - Use of a Diaphragm Type Accelerator Pump 

Use of a diaphragm type accelerator pump such as on Ford 

carburetors in lieu of the piston type on Rochester Products and 

Carter units will prevent leakage. It will require retooling in most 

cases. 

B. Vehicle Selection and Modification 

1. Selection 

Six vehicles were selected from the 20 car group for ECS 

modification. The evaporative emissions and ECS's of these vehicles 

are representative of the 20 vehicle group. The vehicles are shown 

below: 

Table X 

Vehicles for Modification 

ECS 

Car No. Make Year ~ Purge 

1 Ford 75 VI Air Cleaner 

2 Pontiac 75 I Carburetor 

3 Chrysler 75 IV Carburetor 

11 AMC 74 III A. C. Snorkel 

15 Mazda 74 VII (1) 

17 Volvo 74 IX (2) 

(1) Modified Type VII system. 

(2) Fuel injected. Canister for tank vapors. 

It was necessary to return Car No. 3 before completion of the 

test. A vehicle of same make, model and year was obtained for completion 

of the work. This is Vehicle No. 21 in the report. 

2. Current Emissions 

The following table summarizes the original evaporative 

emissions of the vehicles selected to be modified: 
- 32 -

Table XI 

Evaporative Emissions from Six Test Vehicles 

SHED Test Emission Source 

Car 

No. 

1 

2 

3 

11 

15 

17 

21 

Grams % % Air 

Total Diurnal Hot Soak Cleaner 

6.7 50 50 N 

7.5 5 95 y 

17.1 45 55 y 

10.7 5 95 y 

10.6 0 100 y 

7.5 60 40 y 

13.9 40 60 

3. Individual Vehicle Modification 

for Improved Emission Control 

Canister Carburetor 

y Slight 

Slight y 

y y 

N y 

N N 

N 

The most promising hardware based on engineering judgment 

was installed on each test vehicle for the first modification. Additional modifications were then made as necessary to bring the SHED 

test level to 2.0 grams or less. The modifications were prototype 

in nature and not a finished hardware. For example, a manually operated 

clamp on the carburetor vent line performed the job of the carburetor 

vent valve. (Vent valves were on the factory carburetor for Vehicle No. 1, 

3, and 9.) Also, the underhood fan was activated manually. 

The primary goal of this work was to demonstrate an ECS system 

modified to exhibit an emission level of 2.0 grams or less/SHED test. 

However, no attempt was made to test the longevity of the modifications. 

In addition, the modified systems were not optimized for best exhaust 

emissions and/or for driveability. A description of the modifications 

performed on each of the six vehicles is outlined in Tables XII to XVIII. 

Table XII 

MOdification for Vehicle No. 1 - LTD 

Component Factory ECS 

(1) Carbon canister 3 tube Ford (low pressure 

drop) 

(2) Purge 

(3) Carburetor 

( 4) Air cleaner 

Air cleaner 

Leak around choke shaft 

Leak sources at base of 

snorkel and other fittings 

(1) Sketch of cover in Figure 8. 

Modification 

Replaced with 4 tube Vega 

canister with purge control valve. Bottom of 

canister capped. 

Changed to PCV purge. 

Cover fitted over leak 

source(l). 

Sealed with silicone 

sealant. 
- 33 -

FIGURE NO.8 

PROPOSED SEAL FOR CHOKE 

ROD PASSAGE THROUGH AIR HORN 

Cover - CliQS 

..------ Over Walls to 

Seal Shaft 

-----_Walls Cast Into 

Air Horn to Form Seal 

Choke Rod 
- 34 -

Comments: 

A PCV purge was installed after flow tests had indicated 

that air cleaner only and an air cleaner-snorkel combination purge 

were inadequate. This is discussed in Appendix V. The 4 tube Vega 

canister was obtained from a 1974 model vehicle in daily service. 

Photographs of these modifications are shown in Figures 9 and 10. 

Table XIII 

Modifications for Vehicle No. 2 - Pontiac 

Component 

(1) Carbon canister 

(2) Purge 

(3) Carburetor 

( 4) Air cleaner 

(5) Other 

Comments: 

Factory ECS 

Delco 2 tube 

Carburetor 

Small leak around accelerator pump shaft. 

Small leaks 

Modification 

Replaced with 3 tube 

Chrysler canister. 

Bottom of unit capped. 

No change. 

Boot installed around 

shaft. Carburetor 

bowl vented to the carbon 

canister. 

Leak sources sealed with 

silicone sealant. 

Underhood fan installed 

to ventilate underhood 

and lower carburetor bowl 

temperature during hot 

soak. 

Underhood fan used to demonstrate the feasibility of decreasing 

hydrocnrbon vapor generation in the carburetor bowl by lowering bowl 

temperature. No modification of the carburetor purge is required 

in this installation. See Figures 11 and 12 for details of this installation and also Appendix V. 

After completion of tests with the above system, a Vega canister 

was installed and tests were conducted without use of the underhood ventilating 

fan. Results of the tests with this system were also less than 2 grams/test. 
r:::GuR~: 9 COVER OVER CHOKE LINK.\GE TO PREVENT HYDROCAE.BO~ 1&-\KAG::::: 0::.-r THE LTD 

FIGURE 11 FAJ.~ FOR Ul:\'DERHOOD VENTILATION A;ID CARSURLTOR NODIFICATION FOR THE PONTIAC 
F:GURE 12 CARBON Cfu~ISTER (3 TUBE) FOR THE PONTL~C 
- 39 -

Table XIV 

Modifications for Vehicle No. 21 - Chrysle~ 

Component Factory ECS 

(1) Carbon canister One 3 tube 

(2) Purge 

(3) Carburetor 

(4) Air cleaner 

Comments: 

Carburetor 

Leak around accelerator 

shaft. 

Some small leaks 

Hodification 

Two 3 tube canisters in 

parallel were used. 

Bottoms of canisters 

capped. 

No change. 

Boot installed. Second 

carburt:!tur uowl veuteu 

directly to canister. 

Sealed with silicone 

sealant. Barrier installed 

at base of snorkel. 

The large volume fuel tank and the large carburetor bowl volume 

for this car generate too much hydrocarbon vapor for one standard size 

canister to handle. (Purge volume is already high.) Consequently, two 

canisters were utilized. In actual practice, it would be more feasible 

to use one canister with a larger bed. It was necessary to vent the 

second carburetor bowl directly to the canister because the balance tubes 

between the bowls and the air cleaner permitted an excessive amount of 

vapors to enter the air cleaner with a single vent. Details of this 

modification are shown in Figures 13 and 14 and Appendix V. 

Table XV 

Modifications for Car No. 11 - Hornet 

Component Factory ECS 

(1) Carbon canister 2 tube AMC 

(2) Purge 

(3) Carburetor 

(4) Air cleaner 

(1) See Figure 15. 

Air cleaner snorkel 

Leak around accelerator 

pump shaft linkage. 

Several small leaks 

Modification 

Changed to a 4 tube Vega 

with a purge control valve. 

Bottom capped on canister. 

Modified to a PCV system. 

Cap installed over linkage. (I) 

Carburetor bowl vented to 

canister. 

Leaks sealed with sealant. 

Barrier installed at the 

base of the snorkel. 


r:c~RE 15 CARBURETOR BOWI. VENT AND COVER FOR ACCELE?~TOR PU}~ LINKAGE FOR THE HORNET 
- 43 -

Comments: 

Purge flow tests indicated insufficient flow rate from the 

snorkel even with modifications to increase flow. The Vega canister 

used here was obtained from a 1974 Vega which had been driven daily. 

See details of this modification in Figures 15, 16, and 17 and 

Appendix V. 

Table XVI 

Modifications for Car No. 15 - Mazda 

Component 

(1) Carbon canister 

(2) Purge 

(3) Carburetor 

(4) Air cleaner 

(5) Other 

Comments: 

Factory ECS 

Small carbon canister in 

top of air cleaner for 

diurnal cycle only. 

Crankcase 

Bowls vent to air 

cleaner. 

Modifications 

No change in the diurnal 

ECS. Added a 4 tube Vega 

canister for vapors from 

the carburetor bowl. 

Bottom of Vega canister 

capped. 

PCV line used for the 

purge for Vega canister. 

Each bowl individually 

vented to the Vega 

canister. 

No change. 

A fan was installed to 

ventilate underhood during 

hot soak. 

This vehicle utilizes a small carbon canister on the top of the 

air cleaner for storage of diurnal cycle vapors. No change was made in 

this part of the original ECS. The (large volume) two bowl carburetor required separate vents with minimum resistance from each side to transfer 

vapors into the canister. Even then, an underhood fan was used to cool the 

carburetor bowl to retard the rate of hydrocarbon vapor release. Without 

the fan, hydrocarbon vapors from the balance tubes and for drippage in 

carburetor throat caused the SHED level to exceed the 2 gram level. 

For additional details, see Appendix V, and Figures 18, 19, 20, 

and 21. 
F~GURE 16 CARBURETOR HODTFH~ATTON AND !ARRmi r.MJTC:TFR FOR TRP HORN"f<T 
.... -\ 

F IG1JRE 1 7 EARY .. IER AT THE BASE OF THE S~~ORKEL OF TE:: HORNET AIR CLEA.i~ER 


-~ 

00 
(1) 

(2) 

(3) 

(4) 

(5) 

- 50 -

Table XVII 

Modifications for Vehicle No. 17 - Volvo 

Component 

Carbon canister 

Purge 

Carburetor 

Air cleaner 

Fuel tank 

Factory ECS 

Small one tube carbon 

canister. 

Intake manifold 

None - fuel injected. 

No leaks. 

Uses an equalizing valve 

regulating tank pressure 

to about 1.0 psi 

(6. 9 kPa). 

Modification 

Changed to a 2 tube AHC 

canister. 

No change. 

No change. 

Pressure of equalizing 

valve modified to 0.5 psi 

(3.5 kPa). Baffle installed between fuel tank 

and muffler. 

Comments: 

The factory canister was ineffective. (It did not change weight 

during the test period.) Consequently the AMC canister was utilized. The 

high fuel tank pressure resulting from the original equalizing valve 

pressure of 1.0 psig caused hydrocarbon vapors to escape through the gas 

cap and other fittings. The lower pressure for the modified equalizing 

valve corrected this hydrocarbon loss. 

For additional details, see Appendix V and Figures 22 and 23. 

C. Emissions from Modified Vehicles 

1. Evaporative Emissions 

a. Total Evaporative Emissions 

SHED test results for the six modified vehicles averaged 

1.5 grams with a high of 1.9 and a low of 1.1 grams. These data are 

an average of two or more tests and include vehicle background. 

Individual car data are compared with unmodified results as follows: 
CARB00i c,'._\liSTER INSTA.LL\TI00i FOR VO:.VO 
HEr\.T SHII:LD "FOR VOLVO f1_:EL TA~G 

\J1 

N 
• 

Car 

No. 

1 

2 

11 

15 

17 

21 

- 53 -

Table XVIII 

Comparison of "Modified" Emissions 

and "As Received" 

Total Grams/SHED Test 

Make Year Modified As Received 

LTD 75 1.2 6.7 

Pontiac 75 1.9 7.5 

Hornet 74 1.2 10.8 

Mazda 74 1.5 12.2 

Volvo 74 1.1 7.7 

Chrysler 75 1.9 14.0 

b. Adjustment for Background Levels 

The SHED data above were adjusted for background levels using the 

background data from the initial SHED test work (Table V) with the exception of Car No. 15. Because of the exceptionally high initial background 

for this vehicle, it was retested. Background adjustments are shown below: 

Car 

No. 

1 

2 

11 

15 

17 

21 

Table XIX 

Total Evaporative Losses Adjusted for.Background 

Make 

LTD 

Pontiac 

Hornet 

Mazda 

Volvo 

Chrysler 

Before Background 

Adj., Grams 

1.2 

1.9 

1.2 

1.5 

1.1 

1.9 

Background, 

Grams 

0.1 

0.5 

0.2 

0.1 

c. Loss by Mode of Operation 

After Background 

Adj. , Grams 

1.2 

1.9 

1.1 

1.0 

0.9 

1.8 

The hot soak and diurnal losses for the modified vehicles are 

shown in the following table. 
- 54 -

Table XX 

Diurnal and Hot Soak Data 

Car SHED 2 Grams(!) 

No. Make Year Total Diurnal Hot Soak 

1 LTD 75 1.2 0.2 1.0 

2 Pontiac 75 1.9 1.2 0.7 

11 Hornet 74 1.2 0.3 0.9 

15 Mazda 74 1.5 0.6 0.9 

17 Volvo 74 1.1 0.7 0.4 

21 Chrysler 75 1.9 0.6 1.3 

(1) Not adjusted for background. 

2. Exhaust Emissions 

Modifying the ECS caused some changes in the exhaust emissions 

of the modified vehicles. The greatest change was in the CO levels. The 

CO level: (1) decreased for the three vehicles with catalyst beds, (2) increased for one vehicle, and (3) did not change for the remaining two 

vehicles. Only minor changes in the HC and NOx levels were noticed. A 

summary of the exhaust emissions data is shown below: 

Table XXI 

Exhaust Emissions - Modified Vs. As Received 

Exhaust Emissions, 

Car ECS Grams/Mile (1) 

No. Make Year Modified co HC NOx 

1 LTD 75 Yes 4.44 0.52 1.87 

No 6.75 0.54 1. 62 

2 Pontiac 75 Yes 4.05 0.68 1. 36 

No 6.95 0.80 1. 31 

21 Chrysler 75 Yes 13.3 1.10 1. 83 

No 23.2 2.32 1. 98 

11 Hornet 74 Yes 26.9 1.51 1.13 

No 24.5 1.50 1. 24 

15 Mazda 74 Yes 9.90 1. 82 0.65 

No 11.7 2.11 0.88 

17 Volvo 74 Yes 22.6 1.24 1. 58 

No 13.3 0.91 2.15 

(1) Average of two or more tests. 
- 55 -

This program was not of sufficient duration to identify the 

factors causing the above changes. The changes might be due to: 

Alteration in the Induction System 

For each car, the canister was changed as the vehicle was modified. This could change the purge rate and, in turn, may affect manifold 

vacuum. (There were no noticeable effects on driveability during the 

Federal Procedure.) In the case of Car No. 1, 11, and 15, major changes 

were made in the ECS. 

Increase in ECS Hydrocarbon Levels 

The improved ECS in each case requires the engine to handle a 

greater amount of hydrocarbon from the storage systems. This might affect 

the A/F ratio and subsequently exhaust emissions. 

D. Conclusions from Vehicle Modification Work 

The experience gained in modifying ECS systems can be summarized 

as follows: 

1. Larger carbon canisters (activated carbon) were required in 

many cases. 

2. Induction system containment of carburetor hot soak emissions does not appear to be an adequate control for carburetor emissions. 

3. All air cleaner and carburetor leak sources must be eliminated. 

4. Air cleaner and air cleaner snorkel purge systems are inadequate purge systems for a stricter control of evaporative 

emissions.· 

5. Under very severe underhood temperature conditions, it may 

be necessary to minimize heat input to the carburetor by 

mechanical means such as by an underhood fan. 

E. Estimated Costs, Effectiveness, 

and Durability of Modifications 

We have estimated the costs for each of the modifications shown 

in Table IX. Cost data are outlined in Table XXII. The basis for the 

cost data has been estimated as manufacturer's cost times two. In the 

case of carburetor modifications, the indicated figures were obtained 

from Exxon's automotive consultant who is highly knowledgeable in this 

field and has been associated with a major carburetor manufacturing 

company before retirement. The cost of the fan was obtained from an 

automotive manufacturer. In the case of carbon canisters, the cost 

information was obtained from a major manufacturer of these devices. 
TABLE XXII 

ESTIMATED COSTS, EFFECTIVENESS, AND DURABILITY OF ~10DIFICATIO~S 

Modification 

A. Air Cleaner Overflow: 

Control No. 1 - Bowl vent to canister 

Control No. 2 - Ventilate with fan 

Control No. 3 - Barrier at base of snorkel 

Control No. 4 - Smaller bowl 

Control No. 5 - Ventilate with louvers 

B. Canister Overflow: 

Control No. 6 - Increase carbon bed 50% 

Control No. 7 - Increase current purge 

Control No. 8 - Close canister bottom 

Control No. 9 - Control 2 

Control No. 10 - Control 3 

Control No. 11 - Heat purge air 

Control No. 12 - Minimize heat input to fuel 

Control No. 13 - Minimize tank vapor space 

c. Carburetor Leaks: 

Control No. 14 - Seal shafts with boot 

Control No. 15 - Use diaphragm accel. pump 

tank 

Estimated Costs(l) 

$ 

o.so(l) 

17.00(2) 

0.20 

o.2o(l) 

0.0 

4. 00 (3) 

o. 60 (1) ( 4) 

o.2oCl) 

17.oo(2) 

o.2oCl) 

o.soCl) 

1. OO+(l) 

15.0(5) 

o.3oC1) 

1.ooC1) 

Estimated 

Potential 

Effectiveness 

High 

High 

High 

High 

Low 

High 

High 

High 

High 

High 

Fair 

High 

Poor 

High 

High 

Anticipated 

Durability 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Good 

Poor 

Good 

Good 

(1) Basis for estimated cost in case of carburetor and ECS modifications is two times the cost to manufacturer. 

(2) Vehicle retail price estimate from an automotive manufacturer. Capacity- 100 CFM (47.2 dm3/s). 

(3) Cost increment based on cost information from a charcoal canister manufacturer. 

(4) In cases where an existing canister is replaced by the Vega canister, cost is $1.00. 

(5) Not a firm estimate. 

\..., 

C\ 
- 57 -

The estimated costs for the actual modifications for each of 

the six vehicles are shown below. The costs vary from a low of $2.00 

to a high of $25.20. The two vehicles with underhood fans, the Pontiac 

and Mazda, have cost figures substantially above the other vehicles. 

Following these tests, the Pontiac was equipped with a Vega canister to 

replace the fan. Use of this canister also resulted in emissions less 

than 2 grams/test. The cost figures shown in Table XXII were used in 

estimating the modification price for each vehicle. Details for the 

modification costs for each vehicle are given in Appendix VI. 

Table XXIII 

Estimated Costs of Modifications 

Car 

No. 

1 

2 

11 

15 

17 

21 

Make 

LTD 

Pontiac 

Hornet 

Mazda 

Volvo 

Chrysler 

Modification 

Year Costs, $ 

75 2.00 

75 18.30 or 2.30(l) 

74 2.50 

74 25.20 

74 2.00 

75 5.7o(2) 

(1) $18.30 uses an underhood fan. $2.30 system uses 

a Vega canister which eliminates the fan. 

(2) Assumes one canister of larger than current 

capacity would be used in lieu of two units as 

per this work. 

The potential effectiveness and durability of each of the 

modifications is shown in Table XXII. In our opinion, most modifications 

are expected to be effective with a good durability rating. The basis for 

the ratings include personal judgment and field experience with modifications of similar nature. No longevity runs were performed as part of this 

program. 

VI. EMISSION LEVELS OF MODIFIED VEHICLES 

UNDER SEVERE TEST CONDITIONS 

The performance of two of the modified vehicles has been 

evaluated under the severe test conditions of (1) use of a fuel of 

higher RVP than Indolene, and (2) raising the maximum temperature of the 

diurnal cycle. For this work, Vehicles No. 1 and 2 were selected. 

Vehicle No. 2 was equipped with the underhood fan for these tests. 

Test conditions were standard SHED with the exception of the higher 

volatility fuel in one case and the higher temperature range for the 

diurnal in the second case. For the high volatility fuel, butane was 

added to Indolene to raise its RVP from 62.1 to 71.7 kPa (9.0 to 

10.4 psi). Inspections for this fuel are given in Appendix II. 

Standard Indolene was used for the high temperature diurnal cycle runs. 

For these, the diurnal range was 15.6 to 35°C (60 to 95°F) in lieu of 

the standard SHED range of 15.6 to 28.9°C (60 to 84°F). 
- 58 -

The results from this work indicate that Vehicle No. 2, 

the Pontiac, had more reserve storage capacity after modification than 

the LTD, Vehicle No. 1. The 1.4 psi (9.65 kPa) increase in RVP incrP~R~~ 

SHED emissions 1.0 gram for the Pontiac and 4.5 grams for the LTD. Extending the diurnal cycle increased SHED losses 2.1 grams for the Pontiac 

and 3.2 grams for the LTD. Data are summarized below and presented in 

detail in Appendix VII and in Table XXIV. 

Car 

No. 

1 

2 

Table XXIV 

Higher Losses Under Severe Test Conditions 

Make 

LTD 

Pontiac 

Increase Loss, 

Grams/SHED Test 

High High Temp. 

RVP Diurnal 

4.5 

1.0 

3.2 

2.1 

The more severe test conditions described above did not 

significantly affect exhaust emissions with these two vehicles, both 

of which have catalytic reactors to control tailpipe emissions. 

Exhaust emissions data are included in Appendices No. VII"and VIII. 

VII. HALOGENATED HYDROCARBONS IN EVAPORATIVE EMISSIONS 

A brief analytical study has been carried out to measure the 

level of halogenated hydrocarbons in the evaporative emissions from 

leaded fuels. Two halogenated hydrocarbons, ethylene dichloride and 

ethylene dibromide,are part of the lead scavenger package of most leaded 

gasolines. The concentration of these scavengers is about 0.1 wt. % of 

a fuel containing about 3.0 ml/TEL per gallon. The ethylene dichloride is 

present at twice the concentration level of the ethylene dibromide. 

An exploratory analytical procedure was developed to measure the 

scavenger level in the evaporative emissions of a vehicle. For this, 

a gas chromatograph equipped with a sensitive microcoulometer detector 

was used. The source of the evaporative emission was a full size car 

hot soaking in a SHED for one hour. The fuel was a full boiling range 

gasoline containing about 3.0 ml/TEL gallon as Motor Mix. The hydrocarbon 

level in the SHED was 300 ppm C after the hot soak. The concentration of 

ethylene dichloride in the SHED was 0.128 ~g/1. This is about 0.1% of the 

hydrocarbon value in the SHED. We detected but did not quantify the 

ethylene dibromide. The boiling point for the ethylene dibromide is much 

higher than the ethylene dichloride- 131.7°C vs. 83.7°C. 

Because of the low level of scavengers in evaporative emissions, 

it was decided not to conduct additional work in this area at this time. 
APPENDIX NO. I-1 

SURVEY OF CARS AI'l"D LIGHT TRUCKS FOR EVAPORATIVE CO~i':::RO:L SYSTEhS 

F = Full Size 

I = Intermediate 

c = Compact 

Canister Purge Fuel Ian~ \'apor 

Displ. 1.1 of 2 3 4 Purge Line To: ~ear Return 

Make Yr. :1odel Litres Bbls. Tube -- --

Tube Tube Valve? PCV Carb Air Cl. Litres Exh. line? Line? ~ 

Ford 73 I 5.75 4 I I 85.2 ,-

... ~ III 

73 F 6.56 2 I I 85.2 N y III 

73 F 7.03 4 I I 85.2 N y III 

74 I 5.75 2 I I 83.3 y K III 

74 F 6.56 2 I I 83.3 N N III 

75 I 5.75 2 I I 90.8 N N VI 

75 F 6.56 2 / / 90.8 N N VI 

75 I 4.95 2 ..; I 85.2 N N III V1 

~ 

74 c 3.33 1 I I 49.2 N N I 

73 c 1. 60 1 I I 41.6 N N III 

74 c 2.29 2 ..; I 49.2 N N III 

75 I 4.10 1 I ..; 90.8 N N III 

Mercury 73 F 7.03 4 I I 83.3 N y III 

74 F 7.54 4 ..; I 83.3 N y III 

74 I 5.75 2 I ..; 100.3 N N III 

75 I 5.75 2 I I 100.3 N N III 

75 c 3.33 2 I I 49.2 N N I 

73 I 4.95 2 I ..; 85.2 N N III 

Lincoln 75 F 7.54 4 / I 100.3 N y VI 
APPEND IX NO. I-2 

SURVEY OF CARS AND LIGHT TRUCKS FOR EVAPORATIVE CO~TROL SYSTEHS 

F = Full Size 

I = Intermediate 

c • Compact 

Canister Purge Fuel Tank \"apor 

Displ # of 2 3 4 Purge Line To: Near Return 

Make Yr. Hodel Lit res Bbls. Tube Tube Tube Valve? PCV Carb Air Cl. Litres Exh. Line? Line? ~ 

Plymouth 73 I 3.69 1 I I 60.6 ~ :\ IV 

or 75 I 3.69 1 I I 60.6 N -- IV Dodge _, 

75 I 3.69 1 I I 60.6 N X I 

74 F 5.21 2 I I 60.6 N ~ I 

74 F 5.90 4 I I 79.5 N ,,. I ·' 

73 F 6.56 2 I I 79.5 N ~ IV 

73 F 6.56 4 I I 79.5 N K IV 

75 F 7.21 4 I I 79.5 N K I 

0\ 

Chrysler 74 F 6.56 4 I I 73.5 N K IV 0 

I 

75 F 7.21 4 .; I 98.0 N N I 

74 F 7.21 4 I I 98.0 N N IV 

73 F 7.21 4 I I 98.0 N N IV 

AHC 73 c 3.80 1 I .; .; 39.7 N :~ II 

75 I 4.23 1 .; .; 60.6 N N VI 

75 I 4.98 2 .; I 94.6 N N III 

74 I 5.90 4 .; I 92.7 N N III 

74 I 4.98 2 .; .; 64.3 N N III 
APPENDIX NO. I-3 

SL'RVEY OF CARS AJ.'m LIGHT TRUCKS FOR EVAPORATIVE CONTROL SYSTENS 

F = Full Size 

I Intermediate 

c = Compact 

Canister Pur~e Fuel Tank r~--~ C.:-'--

Dis pl. fl of 2 3 4 Purge Line To: ~ear Ret·..:r:-_ 

Hake Yr. Hodel Litres Bbls. Tube Tube Tube Valve? PCV Carb Air Cl. Litres Exh. Line? ' . . L :..:-.e . -:zype 

Chevrolet 75 c 4.10 1 I y I 79.5 y ~ II 

74 I 4.10 1 I y I 79.5 y ,. II ·' 

73 I 4.10 1 I y I 83.3 :-; ,. II ·' 

75 F 5.74 2 I N I 83.3 N :\ I 

75 F 5.74 4 I N I 83.3 N y I 

74 F 6.56 4 I N I 98.4 N y I 

73 F 5.74 4 I N I 98.4 N :-; n· 

73 F 6.56 2 I y I 98.4 N y II 

74 F 5.74 2 I N I 83.3 N ~ I 0"' 

!-' 

Vega 75 c 2.29 2 I y I 60.6 y y IV 

73 c 2.29 1 y I 41.6 y y II 

Monza 75 c 2.29 2 I N I 70.0 y N I 

75 c 2.29 2 I N I 70.0 y N I 

Pontiac 74 F 4.10 1 I N I 95 N N I 

73 I 5.74 2 I N I 95 N i\ I 

73 F 6.56 2 I N I 95 y y I 

73 F 6.56 4 I N I 95 N y I 

75 F 6.56 4 I I 95 N y I 

75 F 6.56 4 I I 95 N y I 

75 F 6.56 2 I I 95 N y IV 
APPENDIX NO. I-4 

SURVEY OF CARS &~D LIGHT TRUCKS FOR EVAPORATIVE CONTROL SYSTID1S 

F = Full Size 

I = Intermediate 

c = Compact 

Purge Fuel Tank Vapor 

Displ. if of 2 3 4 Purge Line To: Near Return 

r-1ake Yr. Model Lit res Bbls. Tube Tube Tube Valve? PCV Carb Air Cl. Litres Exh. Line? Line? ~ 

Cadillac 73 F 7.74 4 .; .; 102 K ~~ I 

75 F 8.20 4 / I 104 N y y Ir 

Olds 73 I 5. 71 4 .; .; 83.3 N N I 

73 F 7.46 4 .; I 79.5 N y I 

74 I 4.10 1 .; I I 79.5 y N II 

75 I 5.74 4 .; I 83.3 N N IV 

75 F 7.46 4 .; .; 98.4 N y IV 0\ 

N 

Buick 74 F 5.74 2 .; I 83.3 N y III 

75 I 4.29 2 I I 91.0 N y I 

75 I 5.74 4 .; I 98.4 N y I 

73 F 7.46 4 .; I 98.4 N y I 

73 I 5.74 2 .; I 83.3 N y I 

73 F 5.74 4 .; .; 98.4 N y III 

75 F 5.74 4 I I 98.4 N y II 

75 I 3.80 1 .; .; 98.4 N N I 
APPENDIX NO. I-5 

S'L'RVEY OF CARS . .'VJ) LIGHT TRL"CKS FOR EVAPORATIVE ENISSIO~ CONTROLS 

Purge Fuel Tank Var::-

Displ. 1; of 2 3 4 Purge Line To: Near Retu:-::. 

~ke Yr. Model Lit res Bbls. Tube Tube Tube Valve? PCV Garb Air Cl. Lit res Exh. Line? Line: ~ 

\w 73 Bug 1.5 1 I ' 40.1 y N :\ 

75 Bug 1.6 1 I I 40.1 ~ ~ 

75 Rab. 1.5 1 I / N ,. y ·' 

Fiat 75 1800 1.8 1 / I ~ y 

75 1300 1.3 1 I I N y ~ 

... 

Opel 74 Hanta 1.9 1 I I 45 y K : 

Hitsubishi 75 Colt 2.0 2 I I N y ::II 

Peugeot 73 504 1. 97 2 I I N N I 

Volvo 74 I 1.98 F .I. I I 59.8 N K I 

C\ 

(.,..) 

Datsun 74 210 2.1 2 Crankcase Storage I 43.9 N N \.III 

British 

Leyland 75 MG 1.8 2 I I 53 N N II 

Toyota 74 2.6 2 I I 45 y N II 

75 2.6 2 / I 45 y N II 

Audi 74 1.5 2 I I 45 III 

75 1.5 2 I I 45 III 

BMW 74 2.0 2 I I 72 I 

Honda 75 1.5 2 I I 41.7 N N I 

Nazda A condenser tank in trunk collects and condenses 

tank vapors. Excess vapor from condenser tank 

goes to PCV valve then to atmosphere. Carburetor 

vapors stored in induction system. 

>ler cedes-:Oenz A compensating tank and a combination valve 

~v~tPm ~ondense vanors and store ex~ess in the 
APPEND IX NO. I-6 

SURVEY OF CARS fu."ffi LIGHT TRUCKS FOR EVAPORATIVE ENISSIOK CONTROLS 

Purge Fuel Tank Vapor 

Displ. II of 2 3 4 Purge Line To: Near Return 

Make Yr. Model Lit res Bbls. Tube Tube Tube Valve? PCV Garb Air Cl. Lit res Exh. Line? Line? ~ 

Ford 75 F250 4.92 1 I I 72.5 N N III 

74 FlOO 3.93 1 I I 72.5 N N III 

International 73 Travall 5.65 I I 79.5 N N v 

0\ 

74 Travall 6.56 I I 79.5 N N v .J::'-

Dodge 75 Van I 87.1 N N v 

Chevrolet, Dodge, Plymouth and Ford light trucks same as cars. 
Inspections 

Reid Vapor Pressure 

Distillation(Z), Temp. 

for ind. D + L: 

IllP 

5 

10 

15 

20 

30 

40 

50 

90 

FBP 

- 65 -

APPENDIX II 

VOLATILITY INSPECTIONS FOR TEST FUELS 

Indolene 

Unmodified Cars 

62.1 kPa 

(9.0 psi) 

36.1°C (9rF) 

48.9°C (120°F) 

55.6°C (132°F) 

62.8°C (145°F) 

69.4°C (lsrF) 

82.2°C (180°F) 

93.9°C (201°F) 

105.0°C (221°F) 

158.9°C (318°F) 

211. 7°C (413°F) 

Modified Cars 

62.1 kPa 

(9.0 psi) 

33.3°C (92°F) 

46.7°C (ll6°F) 

54.4°C (130°F) 

62.8°C (145°F) 

70.6°C (159°F) 

86.1°C (187°F) 

97.8°C (208°F) 

105.6°C (222°F) 

161. 7°C (323°F) 

206.l°C (403°F) 

High RVP(l) 

Fuel 

71.7 kPa 

(10.4 psi) 

31.1 °C (88°F) 

43.3°C (ll0°F) 

52.2°C (126°F) 

61.1 °C (142° .n 

70.0°C (158°I') 

86.1°C (lsr:n 

97.8°C (208°F) 

105.6°C (222°F) 

161. 7°C (323 °F) 

206.l°C (403°F) 

(1) This fuel prepared for the wok presented in part VI of this report. 

(2) ASTM Designation D-86. 
- 66 -

APPENDIX III 

PROCEDURE FOR QUANTIFYING EVAPORATIVE LOSSES 

The procedure for quantifying losses involves collecting the 

vapors and adsorbing them on activated carbon. This is carried out in 

such a manner as to minimize the disturbance of the flow of hydrocarbon 

from the leak source. Vapors are drawn into the collector at a carefully controlled flow rate. They pass through a dryer and then into 

the carbon bed. Non-adsorbed sample is returned to the shed. Provision is made to check the sample leaving the carbon bed for the presence 

of non-adsorbed vapors. A sketch of the equipment is shown in Figure I. 

The flow rate in the collector is critical. Too high a rate 

will lead to excessive losses from the leak source. Too low a rate 

will allow vapors to escape into the shed. The range of operable rates 

is 2.5 to 25 cfh. (71 to 710 L/h). The low rate is effective for 1.0 

g/hr or less and the higher rate for 10+ g/hr. The collector flow rate 

is matched to the source loss rate. If the F.I.D. trace for a hot soak 

shows a high loss rate for the first fifteen minutes of a run followed 

by a low loss rate the remainder of the soak, the collector flow rate 

is set high for 15 minutes and then lowered. 

For most vehicles, the collection equipment can be installed 

prior to the run so as to minimize the length of time the hood is open 

during a run. Small leaks in the air cleaner are sealed before the test. 

The carbon for the collector is activated, non-polar carbon 

of 10-20 mesh. It is dried prior to use. Volume of carbon is varied 

with the amount of vapor to be collected. 
· Vehicle 

Canister 

(Open Bottom) 

From Vapor 

Collector 

- 67 -

APPENDIX Ill 

FIGURE I 

EQUIPMENT FOR QUANTIFYING EVAPORATIVE LEAKS 

Flexible 

Tubing 

Rotameter 

Pump 

Equipment 

Controls 

SHED 

Carbon 

Drierite 

Dryer 

Flow to 

tRotameter 

F .LD. 
Test SHED 

1) SHED 112 2.66 

2) Quantifying Ill 0.12 

3) Quantifying 112 0.08 

4) Quantifying 113 0.18 

5) SHED 113 4.21 

APPENDIX IV 

TABLE I 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Ford LTD 

Year: 75 

No.: 1 

Displ. cu. in./Litre: 351/5.75 

No. Cyl.: 8 

No. Venturis: 2 

Diurnal, Grams Hot Soak, Grams 

A. C. 

Loss From 

Canister Other 

3.06 

1.27(2) 

4.01 

SHED 

3.56 

0.48 

0.48 

1.50 

2.90 

Loss From 

A. C. Canister 

0.0 2.94 

0.0 0.92( 2) 

0.82 3.42 

Other 

Total 

Grams 

Background 

Grams 

Cold Hot Remarks 

6.22 0.74(1)1.39(l) 

6.60 

2.75( 2) 

9.93(3) 

7.11 

(1) High background due to fuel contamination on floor carpet. A fuel can had been placed on the floor of the vehicle 

as an auxiliary fuel tank after SHED Test 113. Spillage from this can occurred some time prior to the background 

test which was run after the SHED testing. 

(2) Heated air tube fron exhaust manifold inadvertently closed off at air cleaner snorkel during this run. Postulated 

that the increase in pressure drop in .the air ~leaner purged the canister to a greater extent than for a normal run. 

(3) Flow rates to collector hydrocarbon beds too high for this run. This tends to pull vapors from air cleaner and 

canister. 
Test SHED 

(1) SHED 111 0.41 

(2) SHED 1!2 0.37 

(3) Quantifying #1 0.46 

(4) Quantifying 112 0.41 

(5) Quantifying 113 0.20 

APPENDIX IV 

TABLE II 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: 

Year: 

No.: 

Pontiac 

75 

2 

Displ. cu. in./Litre: 400/6.56 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A. C. Canister 

6.83 

7.40 

0.20 1. 77 (2) 3.62 (3) 

0.45 1.95( 2) 4.60 0.23 

0.22 0.19 1.61 ( 2) 4.80 0.35 

Background 

Total Grams 

Other Grams Cold Hot Remarks 

7.24 0.50(l) 0.84(l) 

7. 77 :::--

1.77(2) -.c 

6.05 

1.95( 2) 7.64 

1.61 ( 2) 7.37 

(1) Results from the background tests very high. A fuel can had been used in the vehicle after the SHED testing. Spillage 

from this can contributed to high background test which was run after the SHED testing. 

(2) Carburetor leak around accelerator pump shaft. Vapors escaped to the SHED because the leak is unaccessible from a 

quantifying standpoint. 

(3) Collector for hydrocarbon inadvertently omitted. 
Test SHED 

(1) Quantifying fll 0.08 

(2) Quantifying f/2 0.32 

(3) Quantifying f/3 0.17 

(4) SHED f/2 7.30 

(5) SHED f/3 8.63 

APPENDIX IV 

TABLE III 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Chrysler NYer 

Year: 75 

No.: 3 

Displ. -cu. in./Litre: 440/7.21 

No. Cyl.: 8 

No. Venturis: 4 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

o.o 6.46 2.10(l) o.o< 2) o.o<2) 

0.0 3.50 1.34 (l) 0.32(2) o.o<2) 

0.0 3.88 2.01 (l) ·o.o<2> 0.0 (2) 

10.63 

7.76 

Back&round 

Total Grams 

Other Grams Cold Hot Remarks 

2.10(l) 8.64( 2) 0.03 0.13 

1. 34 (l) 5.48( 2) 

2.0l(l) 6.06( 2) 

17.93 

16.39 

(1) Carburetor leak - vapors escape from around carburetor accelerator pump shaft as it passes through the air horn. 

Vapors escape to the shed because the leak is unaccessible from a quantifying standpoint. 

(2) Carburetor bowl maximum temperature during the hot soak is 15 to 20°F (-9.4 to -6.7°C) lower for quantifying r~ns 

than regular SHED tests. This is because hood must be raised to attach hydrocarbon collection equipment when 

quantifying; consequently, less hydrocarbon is lost from the carburetor bowl. 

-...! 

0 
Test SHED 

(1) SHED ill 2.31 

(2) SHED 112 1.50 

(3) Quantifying Ill 0.16 

(4) Quantifying 112 0.33 

(5) SHED 113 1.82 

APPENDIX IV 

TABLE IV 

SL~Y OF EVAPORATIVE EMISSION DATA 

Make: 

Year: 

No.: 

Pinto 

74 

4 

Displ. cu. in./Litre: 

No. Cyl.: 4 

No. Venturis: 2 

122/2.0 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A.C. Canister Other SHED A. C. Canister Other 

4.62 

3.95 

o.o 0.50 0.34 o.o<1) 

o.o 0.0 0.32 o.o<1> 

4.39 

Background 

Total Grams 

Grams Cold Hot 

6.93 

5.45 

1.0 (1) 

0.65(1 ) 

6.21 

0.0 0.16 

Remarks 

(1) Carburetor bowl maximum temperatures are 8 to 12°F (-13.3 to -11.1°C) lower for quantifying runs than for ~HLV tests. 

This is due to heat loss from engine compartment when hood is raised to attach collection equipment for quantifying 

runs. 

... 
Test SHED 

(1) SHED Ill 0.39 

(2) SHED 112 0.58 

(3) Quantifying Ill 0.15 

New Carburetor Installed 

(4) SHED #3 0.28 

(5) Quantifying 112 0.25 

(6) Quantifying {13 0.28 

(7) SHED #4 0.25 

APPENDIX IV 

TABLE V 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Nova 

Year : ---:r4 

No.: 5 

Displ. ~in./Litre: 250/4.1 

No. Cyl.: 6 

No. Venturis: 1 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A. C. Canister 

15.10 

11.40 

0.43 0.32 6.95(2) 0. 71 0.13 

10.04 

0.56 5.96(2) 1.11 o.o 

2.20 5.6oC2) 5.81 (4 ) 1. 82 

1.1. 35 

(1) Carburetor to intake manifold bolts tightened after this run. 

• 

Backgrouad 

Total Grams 

Other Grams Cold Hot Remarks 

15.49 o.o 0.11 (1) 

11.98 

6.95( 2) ....... 

8.67( 3) (2) N 

10.32 

5.96(2) 7.88( 4) (2) 

5.6oC2) 15.71(4) 

11.60 

(2) Carburetor leaks - the carburetor bowl is vented to the atmosphere upon slight pressure increase in the bowl. Other 

leaks occurred around the accelerator pump shaft. Unable to quantify carburetor leaks consequently, vapors enter shed. 

(3) Hot soak losses lower on quantifying runs 1 and 2 than SHED tests because of lower maximum carburetor bowl temperatures. Raising the hood to attach the vapor collection equipment lowered bowl temperature zooF (-6.7oC). 

(4) For this run, vapors from the external vent were collected along with vapors from air cleaner snorkel. The collecting 

system pulled HC from the bowl due to too high a flow rate. 
Test SHED 

(1) SHED til 0.28 

(2) SHED 1!2 0.82 

(3) Quantifying Ill 0.11 

(4) Quantifying 112 0.21 

(5) SHED 1!3 0.41 

APPENDIX IV 

TABLE VI 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Chevrolet Impala 

Year: 74 

No.: --6-

Displ. ~in./Litre: 350/5.74 ~o. Cyl.: 8 

~o. Venturis: 2 

Diurnal, Grams Hot Soak, Grams 

A. c. 

Loss From 

Canister Other 

2.97( 2) 

2.80( 2) 

SHED 

4.69 

4.09 

0.56 

0.52 

5.56 

A. C. 

7.36( 2) 

7.70( 2) 

Loss From 

Canister Other 

1. 71 (2) 

1. 61 (2) 

Total 

Grams 

4.97 

4.91 

12.71 (2) 

12.84(2) 

5.97 

Background 

Grams 

Cold Hot 

(1) (1) 

Remarks 

(1) Background tests for this car were extremely high because of fuel spillage on carpet floor. A fuel can had been 

used as an auxiliary fuel tank after SHED Test #3. Background tests (3+ grams hot and cold) were run after SHED 

testing. 

(2) Collection system pulled vapors from the canister and air cleaner snorkel during the quantifying runs due to too 

high a flow rate. 
Test SHED 

(1) SHED Ill 0.50 

(2) SHED 1/2 0.44 

APPENDIX IV 

TABLE VII 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Plymouth Duster 

Year: 74 

No.: 7 

Displ. cu. in./Litre: 225/3.69 

No. Cyl.: 6 

No. Venturis: 1 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A. C. Canister 

0.73 

1. 32 

Back& round 

Total Grams 

Other Grams Cold Hot Rer.arks 

1. 23 0.66(l) 0.73(l) 

1. 76 

(1) Background results are abnormally high because of gasoline spillage on carpet floor of vehicle from a fuel ca~ 

after completion of SHED tests and before running the background tests. 

'-I 

J:-. 
Test SHED 

(1) SHED Ill 0.90 

(2) Quantifying fll 0.20 

(3) Quantifying f/2 0.33 

(4) Quantifying 113 0.21 

(5) SHED f/2 0.57 

APPENDIX IV 

TABLE VIII 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Buick LeSabre 

Year: 75 

No.: 8 

Displ. cu. in./Litre: 350/5.74 

Diurnal, Grams Hot Soak2 Grams 

Loss From Loss From 

A.C. Canister Other SHED A.C. Canister 

5.16 

1. 88 (l) 1.4o<2>6.52(l) 2.13(l) 

1. 68 (l) 2.58( 2)3.39 0.49 

1.56(2)4.57 0.0 

7.34 

Total 

Other Grams 

6.06 

1.40( 2) 12.13(l) 

2.58( 2) 8.47(l) 

1. 56 (2) 6.02 

7.98 

(1) Hydrocarbon collecting equipment rate too high. Some HC drawn from canister and air cleaner. 

Background 

Grams 

Cold Hot Remarks 

0.06 0.29 

(2) Carburetor leak - carburetor accelerator pump shaft and collar on air horn a very loose fit. No feasible way to trap 

this leak. 

'-.1 

U1 
APPENDIX IV 

TABLE IX 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make~ Vega 

Year: 75 

No.~ 9 

Displ. cu.-in./Litre~ 140/2.29 

Diurnal, Grams Hot Soak, Grams Background 

Loss From Loss From Total Grams 

Test SHED A.C. Canister Other SHED A.C. Canister Other Grams Cold Hot Remarks 

(1) SHED til 0.33 3.49 3.82 o.o 0.57 

(2) Quantifying fl1 0.23 0.45 7.17(l) 7:8S.1,2) 

(3) Quantifying #2 0.18 0.50 0.25(2) 0.93(2) 

(4) Quantifying 113 0.30 0.35 0.16( 2) 0.81( 2) 

(5) SHED ff2 0.21 5.46 5.67 

(1) Vapor collection rate too high in this case. 

(2) ~arburetor bowl temperatures are 15 to 20°F (-9.4 to -6.7°C) lower for quantifying runs than for SHED tests. Hood 

was partially open to accommodate vapor collection equipment. 

'J 

c-
Test SHED 

(1) SHED Ill 0.49 

(2) Quantifying Ill 0.41 

(3) Quantifying 112 0.25 

(4) SHED 112 0.43 

APPENDIX IV 

TABLE X 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: 

Year: 

No.: 

Displ. 

Olds "98" 

73 

li) 

cu. in./Litre: 455/7.46 

Diurnal, Grams Hot Soak2 Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

9.11 

1. 69 (l) 6.92 0.0 

1.67(l) 6.78 0.0 

9.98 

Backs round 

Total Grams 

Other Grams Cold Hot Remarks 

9.60 0.15 0.31 

1.69(l) 9.02 

1.67(l) 8. 70 

10.41 

(1) Carburetor leak around accelerator pump shaft. Vapors esca~ed to the shed because the leak is unaccessible from 

a quantifying standpoint. 

-...,J 

-...,J 
Test SHED 

(1) SHED IF1 0.20 

Carburetor-- to air cleaner 

(2) SHED 1!2 0.73 

(3) Quantifying f!l 0.13 

(4) Quantifying 112 0.12 

(5) Quantifying 1!3 0.18 

(6) SHED 1!3 0.22 

APPENDIX IV 

TABLE XI 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Hornet 

Year: 74 

No.: 11 

Displ. ~in./Litre: 232/3.80 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

12.33 

gasket replaced. Original one cracked and leaking. 

10.11 

6.73(1)19.10(2) 

6.52(1) 4.57 

6.95(1) 4.23 

10.54 

Background 

Total Grams 

Other Grams Cold Hot Remarks 

12.53 0.0 0.11 

10.84 

6.73(l) 25.96( 2) 

6.52(1) 11.21 

6. 95 (1) 11.36 

10.76 

(1) Carburetor leak around accelerator pump shaft. Vapors escaped to shed as leak is unaccessible from a quantifying 

standpoint. 

(2) Flow of hydrocarbon vapors to collector too high. 

-....J 

00 
Test SHED 

(1) SHED Ill 4.61 

(2) Quantifying Ill 1.31 

(3) Quantifying 112 0.86 

(4) SHED 112 3.50 

APPENDIX IV 

TABLE XII 

Su~Y OF EVAPORATIVE EMISSION DATA 

Make: Plymouth Fury III 

Year: 73 

No.: 12 

Displ. ~in./Litre: 360/5.90 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

2.79 

2.70 2.oo(l) o.o 2.41 

1.45( 2) 1. 70 (l) 0.0 1. 65 (2) 

2.26 

Background 

Total Grams 

Other Grams Cold Hot 

7.40 0.07 0.66 

2.00(1) 8.42 

1. 7o(l) 5.63( 2) 

5.76( 3) 

(1) Carburetor leak around accelerator pump shaft. This loss inaccessible from a quantifying standpoint. 

Remarks 

(2) Run No. 3, Quantifying Run 112 is 3.0 grams lower than Quantifying Run No. 1 because the charcoal canister adsorbed 

3.0 grams more for the second run. The hydrocarbon level in the canister decreased from Run Ill to Run 112. 

(3) The total loss for SHED Test 2 is less than for SHED Test 1 because the working capacity of the canister has increased 

during this series of tests. This is indicated by lower canister weights for SHED Test 2 than 1. 

....... 

"" 
APPENDIX IV 

TABLE XIII 

S~UffiY OF EVAPORATIVE EMISSION DATA 

Make: Dart 

Year: 74 

No.: --u 

Displ. cu. in./Litre: 318/5.21 

Diurnal, Grams Hot Soak, Grams Background 

Loss From Loss From Total Grams 

Test SHED A. C. Canister Other SHED A.C. Canister Other Grams Cold Hot Remarks 

(1) SHED Ill 0.16 2.85 3.01 0.0 0.11 

1. 33 (1) 1.33(l) co 

(2) Quantifying ill 0.13 1.82 3. 28 0 

I 

(3) Quantifying 112 0.29 1. 30 (l) 1.57 1. 3Q (1) 3.16 

(4) SHED 112 0.18 2.57 2.75 

(1) Carburetor leak - hydrocarbon leak around accelerator pump shaft. 
Test SHED 

(1) SHED #1 1.25 

(2) Quantifying Ill 0.53 

(3) Quantifying 112 0.79 

(4) SHED 112 0.90 

APPENDIX IV 

TABLE XIV 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Datsun 

Year: 74 

No.: ~ 

Diurnal 2 Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

2.19 

o.o 1.57 0.0 

0.58 1.21 0.0 

1.80 

Backsround 

Total Grams 

Other Grams Cold Hot Remarks 

3.44 0.11 0.20 

2.10 co 

f-' 

2.58 

2.70 
Test SHED 

APPENDIX IV 

TABLE XV 

Sl~~fARY OF EVAPORATIVE EMISSION DATA 

Hake: Hazda 

Year: 74 

~0.: 15 

Displ. ~ in./Litre: Rotary 

Diurnal, Gra:ns Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A. C. Canister 

Background 

Total Grams 

Other Grams Cold Hot Rer::ar~s 

(1) SHED fi 1 0.54 11.56 12.10 0.46(!) 1.10(1) 

(?' _) Quantifying n 1.36 1.,36(2) 7.79( 3) 1. 36 (Z) 10.51(3) 

(3) Quantifying fl2 0.51 1.13 <2> 7.60(3) 1.13 (2) 9.24(3) 

(4) SHED :f2 0.86 11.44 12.30 

(1) Evidence of gasoline spillage in the trunk prior to this work. This would account for high background. 

(2) Carburetor leaks. 

(3) Carburetor bowl temperatures 12-15°F (-11.1 to -9.4°C) lower for quantifying runs than SHED tests because hood 

~as partially open during the hot soak to accommodate the collection equipment. 

co 

N 
Test 

(1) SHED If 1 

(2) Quantifying tfl 

(3) Quantifying i/2 

(4) SHED 112 

(5) SHED 1!3 

APPENDIX IV 

TABLE XVI 

SL~UffiY OF EVAPORATIVE EMISSION DATA 

Hake; Comet 

Year; 74 

No.; 16 

Displ. ~in./Litre: 250/4.10 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

SHED A. C. Canister Other SHED A. C. Canister 

0.21 20.33 

0.16 2.65(1) 11.44 

0.50 2.5l(l) 12.79 

2.12(3) - 14.49 

0.17 14.08 

Total 

Other Grams 

20.54 

2.65(1) 14.25( 2) 

2.51(1) l5.so< 2) 

17.61( 2) 

14.25( 2) 

(1) Carburetor leak around accelerator pump shaft. Inaccessible from a quantifying standpoint. 

Background 

Grams 

Cold Hot 

0.0 0.12 

(2) Several openings in the air cleaner sealed after SHED Test 1!2 which accounts for the lower total emissions for 

these runs than SHED ill. 

(3) Tank drain disconnect fitting leaking during diurnal cycle. 

Re:::arks 

CXl 

w 
Test SHED 

(1) SHED Ill 6.54 

(2) Quantifying 1!1 2.89 

(3) Quantifying 112 0.77 

(4) SHED 112 4.87 

(5) SHED /13 4.49 

APPENDIX IV 

TABLE XVII 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Volvo 

Year: 74 

No.: 17 

Displ. ~in./Litre: 121/1.98 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Gas Cap SHED A.C. Canister 

4.97 

0.37 0.19 1.34(l) 1.63 1.87 0.0 

0.60 0.32 2. 33(l) 1.24 3. 77 0.30 

3.84 

2.62 

Background 

Total Grams 

Gas Cap Grams Cold Hot 

11.51 0.09 0.12 

0. 40(l) 8. 69( 2) 

1.1ll) 10. 50( 2) 

8.31( 2) 

7.11< 2) 

(1) Fuel tank pressure builds up quickly to 1.0+ psig during diurnal cycle and is relieved through the fill cap or 

any other fittings that may leak temporarily. Fuel tank pressure is 1.0+ psi (6.9+ kPa) at beginning of the 

hot soak also. Tank temperature increases 9-10°F (-15.0 to -14.4°C) durinf Federal cycle. 

Remarks 

(2) After SHED test Ill (before Quantifying #1 run), the clamps for the flexible portion of the fill pipe were tightened 

to eliminate a leak. Consequently, subsequent runs are lower in total evaporative emissions. 

(X) 

~ 
Test SHED 

(1) SHED 1!1 3.70 

(2) Q•Jantifying 1fl 0.51 

(3) Quantifying ii 2 0.5Cl 

(4) SP.ED p ,_ 0.56 

(5) SHED f! 3 1.07 

APPENDIX IV 

TABLE XVIII 

SL~~~y OF EVAPORATIVE EMISSION DATA 

Make: Ford 

Year: 75 

~o.: 18 

Displ. ~in./Litre: 460/7.54 

Diurnal, Grarr.s Hot Soak, Grams 

Loss F .co;:; Loss From 

A.C. Canlster Other SHED A.C. Canister 

31.15 

2.23 14.04(2) 4.90 2.13 

15.29(2) 4.38 0.98 

25.75 

29.84 

I3ackground 

Total Grams 

Other Grams Cold llo t IZc:::_.-::·~.s 

34.85(1) 0.0 0.13 

14.04(2) 23.81 co 

~, 

15.29( 2) 21.15 

26,31 

30.91 

(l) Losses higher for this run than subsequent runs because of leaks in the air cleaner, These were scaled for quan~ifyi~g 

and later SHED tests, 

(2) Carb~retor leaks - vapors escape around the linkage for the choke plate and bowl vent to the canister, 
Test SHED 

(1) SHED Ill 0.56 

(2) SHED 1!2 1.15 

(3) SHED 113 0.41 

APPENDIX IV 

TABLE XIX 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: VW 

Year: 75 

No.: 19 

Displ. cu. in./Litre: 97/1.6 (Fuel Injected) 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister Other 

1.43 

1.46 

1.14 

Background 

Total Grams 

Grams Cold Hot Remarks 

1.99 0.69(l) o.ao(l) 

2.61 

1.55 

(1) To verify the high background levels for this car, emissions were monitored for 24 hours. For both hot and cold 

background tests, the rate of hydrocarbon emission had not diminished significantly after 24 hours. Further 

testing showed that essentially all of the hydrocarbon was being emitted from the outside of the vehicle. 

co 

"' 
Test SHED 

(1) SHED Ill 4.41 

(2) Quantifying ill 0.38 

(3) Quantifying 112 0.35 

(4) SHED 112 0.91 

(5) SHED 113 1.09 

APPENDIX IV 

TABLE XX 

SUMMARY OF EVAPORATIVE EMISSION DATA 

Make: Monarch 

Year: 75 

No.: 20 

Displ. cu. in./Litre: 302/4.95 

Diurnal, Grams Hot Soak, Grams 

Loss From Loss From 

A. C. Canister Other SHED A.C. Canister 

6.30 

2.28 3.94(l) 1.86 

1.34 3.26(l) 2.48 

8.62 

6.51 

(1) Carburetor leak around choke plate linkage. 

Background 

Total Grams 

Other Grams Cold Hot Remarks 

10.71 0.0 0.0 

3.94(l) 8.46 

3.26(l) 7.43 00 

....... 

9.53 

7.60 
I. a. 

b. 

c. 

II. 

d. 

APPENDIX V 

TABLE I 

SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES 

Make: Ford "LTD" 

Year: 75 

No.: 1 

Displ. cu. in./Litre: 351/5.75 

Modifications 

Purge from inside air cleaner element. 

Barrier in air cleaner at base of snorkel. 

Choke shaft passage sealed. 

Steps a, b, c 

Air horn to body gasket modified to allow more bowl 

vapors to be stored in air cleaner. 

Evap. Emissions, 

g/SHED Test 

6.1 

9.6 

Remarks 

III.e. Purge to air cleaner snorkel as well as air cleaner. 

IV. 

Measurements were made of purge rates for both an air cleaner and a snorkel purge system. Next. a curve 

of grams removed from canister vs. total purge volume was made. From these data it was estimated that a 

combination air cleaner-snorkel purge system would remove 13 to 15 grams from the canister during the SHED 

preconditioning period (4-LA-4s). This is not an adequate system because the combined diurnal and hot soak 

input to the canister is about 23 grams for the modified vehicle. Consequently~ a PCV purge system was installed 

using a 1974 Vega canister which had been in daily usage up to this time. 

PCV purge with Vega canister. The bottom of the 

canister is capped. An unmodified carburetor body 

to air horn gasket used along with modifications 

b and c above. 

l.l 

1.2 
APPENDIX V 

TABLE II 

Sill-NARY OF EVAPORATIVE EHISSIONS FROH HODIFIED VEHICLES 

~fake: Pontiac 

Year: 75 

No.: 2 

Displ. ~in./Litre: 400/6.56 

~fodifications 

I.a. Vented carb. bowl to canister. 

b. Sealed leak around accel. pump shaft. 

II. Steps a and b 

c. Restriction in line from bowl to canister. 

III. 

d. 

e. 

Steps a, b, c 

Underhood ventilated with a fan. 

Bottom on canister ) 

Evap. Emissions, 

g/SHED Test 

10.5 (diurnal) 

3.4 

1.6 

2.5 

1.7 

Remarks 

Canister dried up before run. 

Fan lowers carb. bowl temp. 

about 30°F (-l.l°C). 
APPENDIX V 

TABLE III 

SUMMARY OF EVAPORATIVE EMISSIONS FROM MODIFIED VEHICLES 

Modifications 

Make: Chrysler 

Year: 75 

No.: 3 

Displ. ~in./Litre: 440/7.21 

Evap. Emissions, 

g/SHED Test Remarks 

I.a. Underhood ventilated with fan. 10.8 (diurnal) 

12.0 (diurnal) 

Fan only lowered c.b. temp. 

5-l5°F. Not blowing directly 

at carburetor. 

II. 

b. Carb. bowl volume lowered 

c. Barrier installed at base of a.c. snorkel. 

d. Accel. pump shaft leak sealed. 

At this point it was determined that one canister would not have sufficient capacity to handle total evap. 

emissions. With a single canister, preconditioning removes 36-40 grams from a fully charged canister. The 

last LA-4 removes only 1 to 2 grams. Combined diurnal and hot soak losses are 50 grams. A Chrysler canister 

from a 1975 vehicle in daily usage was used as a second canister. 

e. Two canisters installed in parallel. I 

f. Second carb. bowl vented directly to canisters. \ 

g. Bottom installed on canisters. 1 

Steps b, c, and d above also used 

(1) 2.1(1) 

2.5 

(1) Exhaust emission data were very erratic. Inasmuch as this vehicle had to be returned to the rental agency, a 

second car will be obtained for further tests. 

\.0 

0 
APPENDIX V 

TABLE IV 

SUMMARY OF EVAPORATIVE EMISSIONS FROH HODIFIED VEHICLES 

:Hake: Chrysler 

Year 75 

No.: 21 

Displ. ~in./Litre: 440/7.21 

I Original ECS 

Original ECS 

II Hodified ECS: 

Hod if ica t ions 

(a) Two canisters in parallel used 

(b) Second carb. bowl vented directly to canister 

(c) Bottom on each canister 

(d) Barrier at base of snorkel 

(e) Accel. pump shaft leak sealed 

Evap. Emissions, 

g/SHED Test 

13.4 

14.6 

1.9 

2.0 

Remarks 

Diurnal- 6.3 g, H.S. - 7.1 g 

Diurnal- 4.4 g, H.S. - 10.2 g 
APPENDIX V 

TABLE V 

SUMMARY OF EVAPORATIVE EMISSIONS FROH HODIFIED VEHICLES 

Hodifications 

I.a. Carb. bowl vented to the canister. 

b. Accel. pump shaft leak sealed. 

Make: 

Year: 

~o.: 

Displ. 

Hornet 

74 

11 

cu. in./Litre: 

II. Steps a and b above - restriction in line from carb. 

bowl to canister. 

c. Barrier installed in air cleaner at base of snorkel. 

III. 

d. 

IV. 

Steps a, b, c above 

Bottom of canister closed. 

ECS modified to a PCV purge system using a 1974 Vega 

canister. Steps a, b, c, and d above also continued. 

232/3.80 

Evap. Emissions, 

g/SHED Test 

3.9 

3.1 

2.5 

1.2 

1.3 

Remarks 
I 

II 

III 

IV 

APPE~1HX V 

TABLE VI 

SUMMARY OF EVAPORATIVE ID1ISSIONS FROM MODIFIED VEHICLES 

Make: Mazda 

Year: 74 

~0.: 15 

Displ. Cu ln./Litre: 80/1.31 (Rotary) 

Modifications 

Both carburetor bowls vented to 

a 3 tube canister (Chrysler). 

Purge is through existing purge 

line to PCV. Original ECS used 

for diurnal. 

Evap. Emissions 

g/SHED Test 

4.8, 3.8 

Remarks 

Hydrocarbon vapors escaping from 

snorkel. 

Next, the modifications indicated below were tested. In each case, the hydrocarbon level from the 

SHED test exceeded 2.0 grams. 

1. Canister moved outside of engine compartment to a cooler environment. 

2. Canister dried up on vacuum pump prior to diurnal and hot soak. 

3. Air cleaner canister closed off and 3 tube canister used for both diurnal and hot soak. 

At this point, additional source determination tests indicated hydrocarbon vapors emanating from 

carburetor throat due to fuel drippage. To alleviate pressure in the carburetor bowl, a fan 

installed to lower bowl temperature by ventilating the underhood engine compartment. 

Modifications for Step I. 

Underhood fan to ventilate 

underhood. 

2.8 

At this point, the 3 tube canist~r was changed to a 4 tube Vega with a purge control valve. (Used 

canister from 1974 Vega.) High diurnal losses in above runs due to tank vapors passing into engine 

crankcase, then through PCV purge line into 3 tube canister. Vapors then moved out of the canister 

into the carburetor bowl and air cleaner through the vent line from the bowl to the canister. The 

purge control valve prevents this migration of vapors into the carburetor bowl and air cleaner. 

Modifications for Step I with 

exception of replacing 3 tube 

canister with a 4 tube unit. 

Fan to ventilate underhood. 

1.8, 1.3 
APPENDIX V 

TABLE VII 

SUMMARY OF EVAPORATIVE EHISSIONS FROM MODIFIED VEHICLES 

Nake: 

Year: 

No.: 

Displ. 

Modifications 

Volvo 

74 

17 

~in. /Litre: 

I.a. Equalizing valve modified so as to relieve fuel tank 

pressure at 0.5 psig. 

b. Baffle installed between fuel tank and muffler. 

c. American Motors canister used. 

121/1.98 

Evap. Emissions, 

g/SHED Test 

0.4 

1.7 

Remarks 

CO and HC exhaust levels 

higher with modified ECS. 
Car 

No. 

1 

2 

21 

11 

- 95 -

APPENDIX VI 

ESTIMATED COSTS FOR VEHICLE MODIFICATIONS 

Make 

LTD 

Pont I :w 

Chrysler 

Hornet 

Modification 

Canister replacement(l) 

Seal-carb. leak 

Barrier-snorkel base 

Air cleaner sealing 

Canister bottom cap 

Total 

Bowl v<:>nt to canistC'r 

SC'dl-<·:~rb. I<>.Jk 

(';tit [HI t•r f,clll om ''·'I' 

A I 1· ,., ''·'""r !I<'<~ I IJif'. 

"'"'' 'l't>ldl 

Canister replacement (3) 

Canister bottom caps 

Bowl vent to canister 

Barrier-snorkel base 

Seal-carb. leak 

Air cleaner sealing 

Total 

Canister replacement( 4) 

Seal-carb. leak 

Bowl vent to canister 

Air cleaner sealing 

Canister bottom cap 

Barrier-snorkel base 

Total 

$ 1.00 

0.30 

0.20 

0.30 

0.20 

$ 2.00 

$ 0.50 

0.30 

0. !0 

I l. 10 

I], 00 ( I . Oil) ( .') 

$18. 30(2. 10) (L) 

$ t,. 00 

0.40 

0.50 

0.20 

0.30 

0.30 

$ 5.70 

$ 1.00 

0.30 

0.50 

0.30 

0.20 

0.20 

$ 2.50 

l'i Mazda Bowl vent to canister (two) $ 1.00 

7.00 

17.00 

0.20 

17 Volvo 

Canister 

Fan 

Canister bottom cap 

Total 

Canister Replacement(S) 

Baffle between tank 

and mufflpr 

Total 

(1) Price difference between 3 tube and 4 tube canister. 

$25.20 

$ 1.00 

1.00 

$ 2.00 

(2) Numbers in parenthesis are costs associated with the Vega canister 

system. 

(3) Price difference between original 3 tube canister and 3 tube with 

SO% larger capacity. 

(4) Price difference between 2 tube and 4 tube canister. 

(5) Price difference between 1 tube and 2 tube canister. 
- 96 -

APPENDIX VII 

HIGH RVP FUEL IN SHED TEST 

Fuel RVP: 71.7 kPa (10.4 psi) 

I SHED Results 

SHED Test, Grams 

Car No. Make Total Diurnal Hot Soak 

1 LTD 6.2 2.6 3.6 

5.2 2.1 3.1 

2 Pontiac 4.4 3.2 1.2 

2.1 0.9 1.2 

2.3 1.3 1.0 

II Exhaust Emission Data 

Grams/Mile(!) 

Car No. Make co HC ~ 

1 LTD 5.19 0.46 1.45 

2 Pontiac 4.69 0.76 1.16 

(1) Average of two tests. 
- 97 -

APPENDIX VIII 

HIGH TEMPERATURE DIURNAL SHED TEST DATA 

Diurnal Cycle: 15.6 - 35°C (60-95°F) 

I SHED Results 

SHED Test, Grams 

Car No. Make Total Diurnal Hot Soak 

1 LTD 4.8 1.9 2.9 

4.0 2.3 1.7 

2 Pontiac 4.2 3.2 1.0 

3.7 2.4 1.3 

II Exhaust Emission Data 

Grams/Mile(l) 

Car No. Make co HC ~ 

1 LTD 5.28 0.44 1. 95 

2 Pontiac 3.83 0.88 1.19 

(1) Average of two tests. 
TECHNICAL REPORT DATA 

(Please read !RS.UUctions on the re~·erse before completing) 

1 ''' I'OH1 r,o _r 3. RECIPIENT'S ACCESSION-NO. 

EI'A-460/ 3-7 6-:::014 -

II II I I I f. • j r; ".1 U B T I T L E 5. REPORT DATE 

1 nves t i galion and Assessment of Light Duty Vehicle May 1976 (Approved) 

Evaporative Emission Sources and Control 6. PERFORMING ORGANIZATION CODE 

----------- --- - 7 AUTHOH(S) 8. PERFORMING ORGANIZATION REPORT NO. 

P. J. Clarke 

~PLRF-OR-MlNG ORG ~-NIZA.TION NAME AND ADDRESS 10. PROGRAM ELEMENT NO. 

Exxon Research and Engineering Company 

P. 0. Box 8 11. CONTRACT I 

Linden, New Jersc•y 

68-03-2172 - 1-- -- - ---- - -- - ---- - ------ - --. -~ ----~- - ----------- 12 SPONSOiliNG ACOl:NCY NAME ANO ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED 

u.s. Environmental Protection Agency Final Report 

O(fict.• of Air and Water Programs 14. SPONSORING AGENCY CODE 

Mobile Source Air Pollution Control 

x~~s~~ggr CoAURt_Ql~ch~§t8_~Y Division 

15. SUPPLEMENTARY NOTES 

To be presented in the form of an APCA paper in June 1976 (Portland meeting). 

16. ABSTRACT -;~ 

This study has assessed the effectiveness of current Evapt'lrative Control Systems 

(ECS) and has shown the feasibility of various hardware approaches which control 

evaporative emissions to a very low level. 

The performance of ECS's in current use was evaluated by using the Sealed 

Housing for Evaporative Determinations (SHED) procedure on twenty 1973-75 cars with 

representative control systems. The measured emissions ranged from 0.5 to 30.6 grams 

per test, and the twenty car average was 8.7 grams per test. 

Hardware was then developed t;o improve ECS performance. Six production vehicles 

were modified to demonstrate the feasibility of improving current systems. These 

modifications were successful in lowering the evaporative emissions to less than 2.0 

grams per test for each of the six modified vehicles. This six car group consisted 

of vehicles manufactured by General Motors, Ford, Chrysler, American Motors, Volvo 

and Mazda; and the costs of required hardware has been estimated at $2, $2, $6, $2, 

$2, and $25, respectively. 

17. KEY WORDS AND DOCUMENT ANALYSIS 

-~---- -- -- -------------~--- -----~ -- a DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI l:icld/Group - -- --- --- ~- ---- ----~--- ------- -- -

Air Pollution Evaporative Emissions 

Motor Vehicles Light Duty Vehicle 

Hydrocarbons Emission Control 

Air Pollution Control Equipment 

1'3. UISTHII:lUTION STATEMENT 19. Sf-CURITY CLASS (Thi.l' Rt•porl) 21 NO. or PAGES 

-100 1---:-· -- -------- Release Unlimited 20. SECURITY CLASS (This page) 22. PRICE 

EPA Form 2220·1 (9·73)