## Technical Report

Recommended Test Procedure

and Supporting Testing Data for the

Evaporative Emissions Leak Test

b y

Peter Smith

Glenn W. Passavant

December 201 3

NOTICE

Technical Reports do not necessarily represent final EPA decisions or positions. They are intended to present technical analysis of issues using data or testing results which are currently

available. The purpose in the release of such reports is to facilitate the exchange of technical information and to inform the public o f technical developments which may form the basis for a final EPA decision, position or regulatory action.

Assessment and Standards Division

Office of Air and Radiation

U.S. Environmental Protection Agency1 I. Introduction

Evaporative emission c ontrol systems have been present on new light

- duty vehicles since the

1971 model year . These systems have gone through several generations of upgrades over the years and

have become more sophisticated and complex a s fuel properties have varied, test procedures have changed, emission standards have increased in stringency , and new requirements have been added to meet greater demands for improved air quality . These onboard systems are currently responsible for capturi ng evaporative emissions produced from gasoline during diurnal , hot soak and running conditions as well as in vehicle refueling situations. Toluene and benzene

, which currently account for about five percent of the tank headspace vapor composition

, have b een linked to possible adverse health effects. 1,2 In addition these compounds and others commonly found in gasoline vapor such as butane and pentane are also responsible for the creation of photochemical smog. Due to these concerns, EPA has sought to increase the capability of these systems to strictly limit the release of these compounds to the atmosphere

.

Over the past several months, the Agency has developed an evaporative emissions leak test procedure which could be used in both laboratory and field conditions to quickly test the integrity of a test
vehicle’s evaporative system. Such a test is independent of On

- Board Diagnostics (OBD ) leak detecti on requirements and as such would not be bound by the limitations and restrictions commonly present in such a monitoring system. The leak test as presently envisioned would be a stand

- alone test designed to find any vapor leaks in the fuel/ evaporative sys tem. This test is not designed to indentify leaks o utside of the fuel and vapor containment portion of the vehicle fuel system.

Past and current wor k at the Agency has found that not all evaporative emissions leaks are being

identified by current OBD systems . This is especially important since these emissions are a potentially significant portion of the evaporative emissions inventory . T his test procedure and accompanying leak

standard could serve as a means to reduce vapor from system leak s in use

. Concurrent with Tier 3 emissions levels it is being proposed that the leak test emission standard be proposed at a value of 0 .02

inches cumulative diameter orifice.

This report w a s p u b l i s h e d f o r c o m m e n t a s p a r t o f E P A ’ s N P R M w h i c h p r o p o s e d t h e l e a k

s t a n d a r d

. 1 N o c o m m e n t s w e r e r e c e i v e d

. T h e f i n a l r e p o r t details the evaporative emissions leak test procedure as presently proposed as well as the vehicle preconditioning necessary prior to undergoing the leak test. It also presents the various testing that has been performed at NVFEL both in the creation of the test procedure as well as supporting data to ensure that the leak test p rovides accurate results on as many different vehicle configurations as possible. Examples of calculations of relative leak orifice sizes are also presented.

II. History of Evaporative Emissions Controls and Standards

Even though present day fuel evaporative emission controls are relatively mature, the development of the present emission standards and related requirements and the control technology applied by the manufacturers has evolved over about 40 years. The activated carbon canister and the

basics of ev aporative system as it is know n today for controlling hot soak and diurnal emissions were required by the for 1971 model year light

- duty vehicles even before the creation of EPA . The purpose of this system is to capture fuel vapors created by the presence or operation of the motor vehicle and store these hydrocarbon vapors in an onboard activated charcoal media known as the charcoal canister. Until recently, m ost manufacturers placed this canister under the hood where it was responsible for capturing the fuel vapors generated when the fuel tank was heated via atmospheric conditions ( diurnal cycle) as

1 S e e A p p e n d i x 1 o f t h e d r a f t R e g u l a t o r y I m p a c t A n a l y s i s s u p p o r t i n g t h e N P R M

. T h i s i s a v a i l a b l e a t http://www.epa.gov/otaq/tier3.htm2 well as the vapors generated from the carburetor float bowls (hot soak) and fu el tank when the vehicle was parked. In uncontrolled vehicles fuel tank and carburetor evaporative emissions were vent ed to the atmosphere. The fuel vapors generated during vehicle operation, known as “running loss” were basically not controlled in early designs.

These early systems did not focus on full vehicle evaporative emissions thus early carbon trap test procedures were deficient in gaining control. Early evaporative systems did not have any type of microprocessor interface for controlling vapor l oads and purge and were controlled via a series of vacuum

check valves , mechanical linkages, and/or solenoids. The canister had a finite storage volume, much like present day systems, and was purged of stored vapors during vehicle operation . Unfortunately, many of these early systems were disconnected or otherwise modified by unknowing motorists thinking these systems had a detrimental effect on the performance or running operation of their vehicle.

Over the past 40 years there have been about five major changes in evaporative emission control requirements. These have involved test procedure changes, more stringent numerical standards , control

of evaporative emissions from other sources on the vehicle

, or control of emissions from various other operating modes. Following the initial requirements for the 1971 model year, noteworthy changes in the regulatory requirements as indicated in the Code of Federal Regulations included: (1) the change from the carbon trap to SHED test method in 1 9 78

, (2) the numerically more stringent 1981 model year hot soak plus diurnal evaporative emission standard s
, (3) enhanced evaporative requirements which phased

- in for

the 1996

— 1999 model years and incorporated multi

- day hot soak plus test requirements and emission

standards , fuel spit back standards, and running loss controls, (4) new onboard refueling vapor recovery requirements which phased in from model years 1998

- 2006, and (5) the Tier 2/MSAT requirements for

2004

- 2010 model years which further tightened the hot soak plus standards, addressed resting losses, and brought in to play consideration of ethanol

- blend fuels. New provisions for “zero evaporative ” vehicles are now in place in California as part of the PZEV allowance in the ZEV program and have recently been

included in the evaporative emission control standards for California’s LEV III program. EPA expects to propose “zero evaporative ” emission standards as parts of its Tier 3 rule to include a more stringent multi

day hot soak plus diurnal emission standard and a canister bleed emission standard and test procedure

.

Computerized emission control system monitoring became necessary when the California Air Resources Board (ARB) mandated that all vehicles sold in that state in 1988 have an onboard diagnostic system to detect problems in the performance of emission control systems . These early systems were

known as On Board Diagnostics (OBD) m onitored the oxygen sensor, the fuel delivery system, engine control module, and the exhaust gas recirculation (EGR) system. If a problem is detected with a vehicle or engine system that is monitored by OBD , the OBD monitor illuminates a Check Engine or M alfunction Indicator Light (MIL) and stores a diagnostic trouble code in memory which can be later retrieved. While some of these codes and problems may be noticed through vehicle drivability changes or other discernible problems with the vehicle performa nce, some are not. Thus, the MIL provides the driver notice of a need to check for a problem in the operation or performance of a given vehicle/engine system based on the diagnostic trouble code (DTC) set in the OBD system

. Vehicle

- based computers also c reated the opportunity for more sophisticated and precise control of canister purge and management of the effects of canister purge on exhaust emission rates.

These controls were further refined with the advent of OBDII which was required beginning in

19 96 with full compliance by 1999. OBDII requirements enhanced the requirements of the original OBD systems and added specific requirements related to detecting problems in the fuel / evaporative control

system

. Current OBD systems are required to monitor f or vapor leaks of various diameters within the

fuel / evaporative control system and to check for proper operation of the purge system, and other general malfunctions related to items such as pressure sensors. It is clear that OBD and the use of the onboard3 computer control system ha s greatly increased the ability of vehicle evaporative and refueling control systems to function more precisely and effectively and to monitor for problems in performance.4 III. Reasons for Creation of an Evaporative Emissi ons Leak Test

At certification current evaporative and refueling emission standards provide reductions in excess of 95 percent over uncontrolled levels when evaluated over the specified test procedures. While programs such as OBD, extended useful life req uirements, and in

- use verification program s (IUVP) testing have improved the overall in

- use performance of these systems, full life durability and performance in off cycle situations remain important objectives.

Even with the upgrades in technology and t est procedures over the past years, it was possible for

a vehicle with a small leak in the fuel/ evaporative control system to meet the hot soak plus diurnal

emission standards. This is because leaks are not expected in certification vehicles and more generally

because the test procedures and standards were not as rigorous and did not require control under all of the

various in

- use conditions which affect evaporative emissions. S ome leak emissions could be

accommodated and the vehicle would still pass the standard. The leak detection requirements of the

OBD II regulations have helped to focus more attention on preventing leaks over the vehicle life.
However, from an in

- use perfor mance perspective OBD alone is not sufficient for at several reasons

. First, OBD systems do not operate under all conditions and do not require that the owner/operator seek a repair if a MIL is indicated. While repairs are far more likely areas with insp ection /maintenance ( I /M)

programs, repairs are not always made and if so they may well wait until the I/M check is due. Second, is the issue of OBD system readiness. There are operating circumstances when an OBD system is not required to monitor the evaporative system . These are commonly termed g lobal disables and deficiencies. For example

, global disables include specifications on outside air temperature, elevation (i.e., barometric pressure), and tank fuel volume. Deficiencies include manufacture r specific exceptions provided on a

case

- by

- case basis when the system cannot meet the OBD monitoring requirements either due to an element of fuel/evaporative system design or if there is some operating condition in which the OBD leak detection methodolog y does not operates reliably in the sense of not giving false fails or false passes. If the vehicle is operating in one of these “disable” or “ deficiency ” conditions the OBD system will not run and not detect a leak. Third, OBD systems are not required t o detect leaks of less than 0.020”. While the prevalence of these very small leaks is not known

, it is reasonable to project that they are at least as prevalent as larger leaks. L imited data indicates that the leak emission rate for vehicles with leaks less than a 0.020” diameter orifice is not significantly less than at 0.020”. Thus, they are potentially significant.

Tier 3 evaporative emission standards are intended to allow for essentially zero fuel vapor

emissions over the vehicle useful life. Full l ife Tier 3 evaporative emission standards coupled with upgraded OBD will help to encourage focus on designs and technology which will improve in

- use durability. However, a vehicle with a vapor leak in the fuel evaporative emission system will emit VOCs

at a greater rate than anticipated from the “zero evaporative ” technology on which the proposed Tier 3 evaporative emission standard is based. To help insure that the reductions envisioned by proposed Tier 3 evaporative emission standards are achieved in

- use , EPA is considering an evaporative emissions leak test procedure and standard . The leak emission standard w ould help to ensure added focus on efforts to improve in

- use durability by reduc ing the diameter and prevalence of leaks

.

The remainder of this memorandum covers the following areas. Section IV, which follows next,

discusses current leak measurement meth o ds and work done by EPA. Following this is a presentation on the basics of the recommended test procedure, (section V), a validation of the recommended test procedure by testing on some more unusual fuel/evaporative system configurations (section VI) , and finally a n assessment of the leak test procedure results to several key pre

- conditioning variables (section VII)

.5 IV. Measurement Methods

At present, at least two different methods exist for determinin g evaporative system leaks . The

first and more commonly used method is via positive pressure and flow measurement of the system. In this instance, the evaporative system is pressurized with a gas (normally inert nitrogen) to a set and measured pressure. In

- line with the test apparatus is a flow meter designed to measure the flow of the test gas being introduced to the evaporative system. Once the system is pressurized to a certain level, the resulting gas flow is measured and compared to that at known conditions and leak sizes. In this manner, any resultant leaks on the vehicle’s evaporative system are determined.

The second manner in which leaks are measured and quantified is through a proc ess of measured vacuum decay. In this method, a certain amount of pressure or vacuum is placed on the evaporative system and then monitored as to how long the evaporative system takes to release any such pressure or vacuum. By comparing this rate to that of know n decay rates f or an identical system, any such leak present in the test system can be quantified.

a. Pressure and Flow Measurement Systems

The most common devices for finding evaporative leaks are based on the pressure and flow measurement basis. There are many versions on the market today with some being used in individual

states’ I / M programs. Most of these devices will use an external source of inert test gas so as to mitigate

the comb ustion hazard of mixing oxygen with flammable hydrocarbon vapors.

i. Current Production Versions

Two examples of current production leak testers are shown in Figures 6 and 7. They are the

EELD (Evaporative Emissions Leak Detector) 500 tester produced by Snap On and the Delphi 2010 produced by Delphi. Both devices O perate on the same principle of flow and pressure measurement into

the test vehicle.

Figure 1

– Snap On EELD 500 Tester Figure 2

– Delphi 2010 Evaporative Tester

The Snap On unit has the capability to also introduce smoke into the test vehicle’s evaporative system in order to determine not only the resultant leak size but also its location. The Delphi unit also has an optional smoke generation feature . Both machines are similar in that they also provide for individual calibration of the units. The EELD performs a calibration check each time the unit is switched on, while the Delphi unit comes with a test tank and calibrated or ifices to perform a field calibration of the unit.6 Both devices are portable with onboard rechargeable batteries or 110V power and both devices pressurize

the evaporative system with up to 18” of water pressure.

The EELD unit was extensively tested by NV FEL staff over the course of several months as well as compared to the EPA Test Console created using laboratory grade equipment also designed to measure

leaks. While we used this tool in our evaluation program and in developing the test procedure,

manuf acturers can use any tool or other method which meets the requirements of the regulations.

Several tests were conduct ed so as to ascertain the EELD ’s performance. These test units were purchased by NVFEL for testing through normal distribution channels. All measurements were obtained using a series of stainless or brass orifices obtained from O’Keefe Controls. The orifices tested ranged in sizes under 0 .010 to over 0 .050. Figure 8 shows the relative performance between two different EELD units, seri al #’s SA 3890 and SA 3888

, respectively. In addition # SA 3890 was also tested in the same manner on a different day to determine any day to day variability with the units. Upon analysis of the results, it was noticed that both SA 3890 and SA 3888 units underestimated the size of the resultant evaporative leak on the order of 0 .003

- 0 .004” as compared to the orifices obtained from O’Keefe

Controls . Discussion with the parent company Star Envirotech, which produces the unit for Snap On, resulted in the procurement on a new prototype test device which did not include the smoke feature. The performance of this new version is indicated by the “New Board” data on the graph in Figure 3 . Its performance was greatly improved versus the product ion versions. Upon further testing it was realized

that the flowing of smoke through the test orifice displaced a certain volume of measured test gas which

caused the units to indicate a leak size less than actual.

Figure 3

– Production EELD Samples with Smoke vs. Non Smoke Version

As seen in Figure 4, t he EELD without the smoke feature was also compared directly to the

results obtained via the NVFEL Test Console.7 Figure 4

– Comparison of EELD Non Smoke Board vs. Test Console

In all instances, the EELD version without the smoke compared favorably to the Test Console. Some variation was seen at the extreme ends of the orifice sizes, primarily under 0.010” and over 0.045”. Since leaks at these ranges were not of concern for the ongoing test program, the EELD was used for validation of the test procedure due to its ease of use and fast reporting of test results. The raw data from the testing is presented below in Figure 5

. It is important to note that in the range of interest 0 .010

- 0 .030, that both the Test Console and the EELD displayed similar errors in the calculation of the test orifice size. This could possibly be due to slightly inconsistent sizing in the test orifi ces themselves leading to even better unit performance once these sizing errors are taken into account.

Figure 5

– Data Obtained from Comparison of Test Console and EELD8 ii. NVFEL Constructed Device

The EPA c onstructed test device is also base d on the principle of flow and pressure measurement. The test device (Test Console) was built using a Honeywell FP200 pressure transducer calibrated in the range of 0

- 2.5 psi as well as Teledyne Hastings HFM

- 300 flow meter s calibrated in ran ges of 0

- 2 slpm

and 0

- 10 slpm. Figure 6 depicts the flow layout and construction of the test console.

Figure 6

– NVFEL Test Console Flow Diagram

The equation presented in the test procedure (see below ) was developed through NVFEL testing. It allows the calculation of an effective orifice leak diameter in inches based on the type of test gas being used, the temperature of the test gas, as well as the measured pressure and flow of the test gas through the

T est Console. Figure 5 shows the correlation between the test console equation constants and empirical data obtained from a wide range of O’Keefe orifices. In all measurements, error was l ess than 3 percent
from actual to measured values.

The overall equation as presented in the test procedure was then implemented in the control software for the Test Console. Flow and pressure values were recorded by flowing N 2 gas through the test console and test orifice. A variety of orifice sizes were tested rang ing from 0.008” to 0.031”. The pressure was varied from 0.25 to 1 psi and the corresponding flow recorded at each pressure point. The orifice diameter was calculated via software using the supplied equation and plotted in Figure 7.9 Figure 7

– Validation of Test Console Equation Constants10 The actual orifice size is modeled as a straight line and is indicated as the orifice size

- TGT on the plot legend from Figure 8 . For all orifice sizes tested, the equation deviated from the actual value by

less than 0 .001 ” in actual reading. Good correlation was seen throughout the pressure range s tested.

Figure 8

– Validation of Supplied Test Proce dure Equation

b. Vacuum or Pressure Decay Measurement Systems

Most commonly available evaporative test devices operate on the principle of pressure and flow

measurement to find evaporative system leaks. At the time of the report, initial conversations were underway with Mahle Test Systems regarding their new tester for evaporative systems that operated on the principle of drawing a fixed vacuum on the evaporative system and measuring the d ecay over a short period of time. Currently such a system is being used in several OEM assembly plants to find leaks prior to the vehicles being fueled. According to Mahle, proprietary algorithms allow leak detection down to

0 .010” and smaller can be fou nd on less than 0 .5 psig of vacuum. Typical test times are on the order of

10

- 30 seconds. No vacuum or pressure decay systems were available for evaluation. 

### 0 0.005

0.01 0.015

0.02 0.025

0.03 0.035

0 0.5 1 1.5OrficeDiameter(in)

Test Pressure (psi) 

# Evaporative Test Equation Results

0.008

.008_TGT

0.012

.012 TGT

.014 TGT

0.02

.020 TGT

0.025

.025 TGT

0.031

.031 TGT

.008_211 V. Recommended Test Procedure

Based on our developmental work with the EPA NVFEL Console and the Snap

- On EELD 500 (no smoke) meter, EPA developed a draft recommended test procedure. The proposed test procedure for

fuel /evaporative system leak testing provided in Code of Federal Regulation format is as follows . It does not require the use of any spe cific instrument.

§86.167

- 18 Leak test procedure.

(a) Scope . Verify that there are no significant leaks in your fuel storage system using the leak test described in this section. Perform this check as required in the standard

- setting part.

(b) Measuremen t principles . A leak may be detected by measuring pressure, temperature, and flow to calculate an equivalent orifice diameter for the system. Use good engineering judgment to develop and implement leak test equipment. Your leak test equipment must meet the following requirements:

(1) Pressure, temperature, and flow sensors must be calibrated with NIST

- traceable standards.

(2) Correct flow measurements to standard temperature and pressure of 20 °C and 101.3 kPa.

(3) Leak test equipment must have the abi lity to pressurize fuel storage systems to at least 4.1 kPa and

have an internal leak rate of less than 0.2 0 slpm.

(4) You must be able to attach the test equipment to the vehicle without permanent alteration of the fuel

storage or evaporative emission control system s

.

(5) The point of attachment to the fuel storage system must allow pressurization to test system integrity of the fuel tank and fuel and vapor lines reaching up to and including the gas cap and the evaporative

canist er. An example of an effective attachment point is the evaporative emission system test port

available on some vehicles.

(c) Leak test procedure . Test a vehicle’s fuel storage system for leaks as follows:

(1) Fill the vehicle’s fuel tank to 40% capacity.

(2) Soak the vehicle for 6 to 24 hours at a temperature of 20 to 30 °C and maintain this temperature throughout the leak test.

(3) Before performing the test, purge the fuel storage system of any residual pressure, bringing the system into equilibration w ith the ambient.

(4) Seal the evaporative canister’s vent to atmosphere and ensure that the system purge valve is closed.

(5) Attach the leak test equipment to the vehicle.

(6) Pressurize the fuel storage system with nitrogen or another inert gas to at lea st 2.4 kPa. Use good engineering judgment to avoid over pressurizing the system.

(7) Maintain gas flow through the system for at least three minutes, ensuring that the flow reading is

stable for an effective leak diameter of ± 0.002 inches.12 (8) Use the fo llowing equation, or a different equation you develop based on good engineering judgment, to calculate the effective leak diameter, D eff

.



## ( ) ( ) ( ) 0.5057

gas
eff

12 12 

### 0.2153

960 459.67 V D
PP PP

G T    

= ⋅
−⋅+

⋅ ⋅ +  

Where:

D eff = Effective leak diameter, rounded to the nearest 0.01 inch.

V

gas = Volumetric flow of gas (scfh).

P 1 = Inlet pressure to orifice (psia).

P 2 = Atmospheric pressure (psia).

G = Specific gravity of gas at 14.7 psia and 60°F.

T = Temperature of flowing medium (°F).

(9) You may perform any number of replicate tests; howeve r, you must perform the same number of tests at the same attachment points for every vehicle from a given model year. The average value of replicate tests is the official result for a given vehicle.

( 10 ) You may use special or alternative test procedures as described in 40 CFR 1065.10(c). For example, a manufacturer may use a vacuum

- based instrument or approach if it can demonstrate correlation and

meet th e requirements of the applicable regulations.

(d) Equipment calibration . Use good engineering judgmen t to calibrate the leak check device.

For example, you may compare measured and calculated values to a calibration orifice such as that defined as an O’Keefe Controls Co, Type B precision

- machined brass or stainless steel orifice having a gas flow path dep icted in the following figure:13 

### Figure 1 of §86.167

Validation of Test Procedure

There are many minor design and architecture variations, but essentially all vehicle evaporative control systems involve the use of a carbon canister to capture vapors from the gasoline tank and a vent and purge solenoid system for refreshing the storage c apacity. Leak detection approaches as part of this system are based on either natural vacuum or an integrated pump and orifice approach. The leak detection instruments described above are commercially available and in use in the auto industry today; there is a high degree of confidence in their capability to detect leaks when applied properly for the intended purpose. This was confirmed during the testing we conducted on a number of different production vehicles in developing this recommended practice. Fo r further validation purposes, we looked at several unique design and test conditions to confirm the utility of the test equipment and test procedure in these applications. These included testing on a Ford F150 with the “No Cap” style fuel fill, a Chrysle r 300 equipped with both an ESIM valve and a “No Cap” style fuel fill, a Ford E350 cargo van with a fuel tank larger than 20 gallons and a Honda Accord . For all the vehicles tested, the following EELD tester procedure was used.

Evaporative Emissions EELD Tester Attachment Procedure

1. Connect EELD Tester to Test Vehicle

a. Locate p urge s olenoid (typically located under hood nearby intake manifold or throttle body)

b. Remove vapor line on fuel tank side of p urge s olenoid (various clips can be used)

c. Insert hose adapter and modify as necessary to ensure a proper seal to the vapor line

2. Attach Scan Tool to OBD port

a. Verify engine size and details from under hood emissions label

b. Follow options and screens necessary to allow tool to control evaporative vent solenoid

c. Arrive at v ent s olenoid command screen (typically under special tests or emissions test

sub

- menus)

3. Power up EELD Tester

a. Attach N2 gas to tester (set to 85

- 100 psi inlet)

b. Select menu for proper gas while tester is booting (must do this at the righ t time or tester will default to AIR for test medium) Menu selection is done by pressing display select on the side of the tester until N2 is displayed. Tester can accommodate N 2 , CO 2 and air for

test gas.
4. Conduct Test

a. Command tester to flow nitrogen to test vehicle.

b. Close v ent s olenoid on test vehicle using the scan tool14 c. Monitor flow and pressure in tank and read resultant orifice leak size on tester screen. (Test value will start off high and stabilize to a final reading as fuel tank is pressurized.

Te st runs for 5 minutes and then tester will turn off. To continue flowing nitrogen simply command the EELD to test again)

a. Ford “No Cap” System

The Ford vehicle tested was a 2011 Ford F150 pickup VIN# 1FTFX1CT5BFA93342. The vehicle had 252 miles on it at the time of testing. The fuel tank was drained and filled to 40 percent with

cert ification fuel. The vent solenoid was commanded by a Geni sys OTC scan tool. The system was pressurized by disconnecting the evaporative line from the purge solenoid and pressurizing the system via this interface point. All testing was done with the updated version of the EELD500 which did not in clude the provisio n for smoke. The inlet pressure for nitrogen test gas for the EELD was set to 90 psi. Readings were taken approximately four minutes after the start of each test. Seven test repeats were run with the tester disconnected and the system allowed to vent fo r several minutes between tests.

This vehicle was chosen in order to asses any differences in testing necessary to accommodate Ford Motor Company’s “No Cap” style of fuel tank system. In all cases, a well sealed system was

indicated. The indicated leak value on the EELD was at .000 at four minutes duration for each of the seven tests. It took approximately 3.5 minutes for the tester to pressurize the tank and indicate a .000 reading. The final pressure indicated by the EELD was relatively consistent as well

, with readings ranging from 17.3

– 17.6 in ches water . No changes to the test procedure were necessary for this application.

b. Chrysler “ No Cap” ESIM System

The next configuration tested was a 2012 Chrysler 300 VIN# 2C3CCACG2CH266160 equipped with Chrysler’s version of the “No Cap” fuel filler system as well as the ESIM style of vent valve. The vehicle had 1942 miles on it at time of testing. The updated EELD unit (no smoke ) was used to test this

vehicle. The fuel tank was drained and filled identically as the F150 previously tested. Because of the year of the vehicle, available scan tool equipment was unable to communicate with the vehicle’s ECM. In all testing, the vent line was disconnected from the ESIM valve . The evaporative system w as pressurized via the line going to the under hood purge solenoid. The ESIM valve and charcoal canister were located behind the right hand rear wheel well liner.

This vehicle was chosen in order to asses any differences in testing necessary to accommodat e Chrysler’s “No Cap” style of fuel tank system as well as any special procedure s needed in testing a system which did not have a traditional solenoid controlled vent valve. In all cases, a well sealed system

was indicated. The indicated leak value on th e EELD was at .000 at four minutes duration for each of the seven tests. It took approximately 2.0 minutes for the tester to pressurize the tank and indicate a .000 reading. The final pressure indicated by the EELD was relatively consistent as well with readings ranging

from 17.4 to 17.5 in ches water . No changes to the test procedure were necessary for the application with the exception of the understanding that sealing the vent line from the ESIM valve acted in a similar fashion as commanding the vent v alve closed on a traditional system. Figure 9 below shows the “No Cap” style of filler system. The Ford system is similar with the exception that it does not have the sealing cover for the filler inlet pipe.15 Figure 9

– Chrysler 300 “No Cap” Fuel Filler Inlet

d. Fuel Tank Systems Greater Than 20 Gallons

The vehicle tested was a 201 2 Ford E350 Passenger Van VIN# 1FBSS3BL3CDA75451 . The

vehicle had 3452 miles on it at the time of testing. The fuel tank was drained and filled to 40 percent
certification test fuel. The capacity of the fuel tank was 40 gallons as indicated in the owner’s manual and

via measurement of the external tank dimensions. The vent solenoid was commanded by a Geni sys OTC scan tool. The system wa s pressurized by disconnecting the evaporative line from the purge solenoid and pressurizing the system via this interface point. Figure 1 0 shows the EELD attachment point. All testing was done with the updated version of the EELD500 which did not include the provision for smoke. The inlet pressure for nitrogen test gas for the EELD was set to 90 psi. Readings were taken approximately

four and a half minutes after the start of each test. Seven test repeats were run with the tester disconnected and the system allowed to vent for several minutes between tests.

Figure 10

– Ford E350 EELD Attachment Point

This vehicle was chosen in order to asses any differences in testing necessary to accommodate tank sizes larger than 20 gallons

. The indicated leak value on the EELD ranged from 0 .001 to 0 .005 for each of the seven test repeats for this vehicle. There was indication t hat the default five minute tes t time on the EELD was not sufficient for this vehicle to fully pressurize such a large tank volume leading to the variation in “found” leak values. In addition, it was seen that the variation in indicated leak values was16 affected by the depressurize time between tests. In prior testing, two minutes was allocated between tests

to allow the evaporative system and fuel tank to equalize to atmospheric pressure with an open vent valve and fuel cap. With the larger tank system of 40 gallons two minutes was se en as not enough depressurization time. If the subsequent test was started within two minutes

, the ramp time down to the

indicated leak value was faster than that measured between tests with more than a two minute wait time. Figure 1 1 shows this effect. Based on th is testing , it is recommended, when testing large tank sizes, to wait at least 5 minutes between test intervals if repeated testing is necessary as well as to test longer than 5 minutes (in the case of the EELD) in order to give larger system s the appropriate pressurization time needed to achieve representative results. It should be noted that even though the larger system took longer to fill and achieve a final reading, indicated leak values were within .004” of each other after three minutes of testing.

Indicated Leak Value Indicated Leak Value

Test Time (min) w / 2 Min Wait w / 5 Min Wait

1 0.014 0.021

2 0.006 0.01

3 0.002 0.006

4 0.001 0.004

5 0 0.002

Figure 11

– EELD Indicated Values on 40 Gallon Test Tank

e. Honda Produced Fuel Systems

The Honda vehicle tested was a 2007 Accord sedan VIN# 1HGCM56727A141399. The vehicle

had 123821 miles on it at the time of testing. The fuel tank was drained and filled to 40 percent with

cert ification test fuel. The vent solenoid was commanded by a Vectronix Mastertech scan tool . The system was pressurized by disconnecting the evaporative line f rom the purge solenoid and pressurizing the system via this interface point. All testing was done with the updated version of the EELD500 which did not include the provision for smoke. The inlet pressure for nitrogen tes t gas for the EELD was set to

95 p si. Readings were taken approximately four minutes after the start of each test. Seven test repeats were run with the tester disconnected and the system allowed to vent for several minutes between tests.

This vehicle was chosen based on concerns initiall y expressed by Honda regarding the interface of the leak detection test methodology with their OBD leak detection scheme. We assessed a Honda17 vehicle equipped with a Honda evaporative control system using a solenoid controlled vent and purge

valve. In a ll cases, a well sealed system was indicated. The indicated leak value on the EELD was at .000 at four minutes duration for each of the seven tests. It took approxi mately 3 minutes for the tester to pressurize the tank and indicate a .000 reading. The f inal pressure indicated by the EELD was relatively

consistent as well with readings ranging from 17.5

– 17. 7 in ches water . No changes to the test procedure

were neces sary for this application.

VI. Tested Vehicle Variables for Preconditioning

Current preconditioning required prior to conducting the evaporative test is as follows:

1. 6

- 24 our soak at 20

- 30 ° C prior and during testing

2. 40 percent fuel fill capacity using Tier III certification fuel (9 RVP E15)

3. Purge of any residual fuel tank pressure prior t o testing

The cold soak and fuel tank fill level is consistent with the preconditioning needed for the FTP test so as to minimize any additional testing burden associated with running the leak test. Prior to setting these preconditioning requirements, sev eral factors that were thought to possibly influence the leak test results were investigated. These factors were the fuel fill level, the fuel tank temperature, test vehicle inclination and the leak location relative to the insertion point of the leak tes ter. These factors were investigated by using a first generation Snap On EELD500 tester . The EELD had the provision to introduce smoke into

the evaporative system but was not filled with the smoke solution for this testing . The vehicle used for all

of t he preconditioning investigation was a 2006 Chevrolet Silverado, VIN# 1GCEK19B6GZ154114. This vehicle had approximately 110,056 miles on it and the vent valve was controlled via a GM Tech 2

service tool. An evaporative test port was located under the hoo d and was used as an attachment point for

the EELD tester.

a. Fuel Fill Level

To investigate the influence of fuel fill level on the leak test, the test vehicle was drained and

filled to various levels of cert ification test fuel. The levels investigated were 10, 40, 80, and 100 percent tank capacity. Each test was performed at a temperature of 25 ° C. At each fuel level, seven repeat tests were performed with the EELD tester. After each reading the tester was removed and t he system was allowed to depressurize for several minutes. A simulated leak was created by tying in a 0 .020 stainless O’Keefe orifice at the purge valve. The results are presented below in Figure 1 2 . The error bars represent the inherent repeatability o f the unit. It was felt that the EELD was accurate to a +/

- .001” reading while operating under the testing conditions. While the 10 percent fill levels had the highest indicated leak reading, on average these were .001” or less than what was indicated a t the 40 percent fill levels. This difference was also within the accuracy of the EELD unit. So based on the collected data, it was determined that the fuel fill level had a minimal, if any, effect on the test reading.18 Figure 12

– EELD Readings for Several Fuel Fill Levels

b. Fuel Temperature

To investigate any fuel temperature effects on the leak test, the same test vehicle was used and

filled to a 40 percent fill level with cert ification test fuel. The temperature of the vehicle was varied by subjecting it and the fuel to an overnight soak at the prescribed temperature in a VT SHED. The three temperatures tested were 25, 30, and 35 ° C. Data obtained from the t esting is presented in Figure 1 3 . As

can be seen

, most values are within the accuracy of the EELD, however those obtained at 35 ° C show a slight trend for higher readings. Since the existing FTP preconditioning was from 20

- 30 ° C, it was determined to stay within that range. In this ra nge, fuel tank temperature did not affect the EELD readings. 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.019

0.02

0 1 2 3 4 5 6 7 8Indicated Orifice Size



## Test Point Fuel Tank Fill Effects (25 C, 0.020" )
0.020" Implanted Leak

40% Fill

10% Fill

80% FIll

100% Fill19 Figure 13

– EELD readings for Various Fuel Temperatures

c. Vehicle and Tank Inclination

Another factor investigated was the inclination of the test vehicle. Again, the same vehicle was

used and filled to a 40 percent level with cert ification test fuel. The test vehicle was then placed on a two post hoist and the appropriate lift arms positioned to cant the vehicle in various directions. The

inclinations tested were 5 ° left and right (roll) , as well as 5 ° front and back (pitch) . All readings for the EELD were within the accuracy of the unit for the various vehicle inclinations tested. These results can be seen in Figure 1 4

. 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.019

0.02

0 1 2 3 4 5 6 7 8Indicated Orifice Size



## Test Point Fuel Temperature Effects (25

- 35 ° C )
0.020" Implanted Leak

25C

30C

35C

Most measurements within accuracy of unit20 Figure 14

– EELD Readings for Various Vehicle Inclinations

d. Leak Location

The last possible influencing factor tested was the location of the leak relative to the insertion or

test point of the EELD. In these tests, the identical test vehicle was used and filled to a 40 percent fuel

level with cert ification test fuel. In all cases, the EELD attachment point remained consistent at the under

hood evaporative test port. The location of the leak was varied between the purge valve (near to the test attachment point) and the top of the fuel cap (far from the attachment point). The re sults are presented in Figure 15 . With in these results a definitive trend could be observed. The EELD i ndicated higher leak values when the orifice was placed near the test attachment point versus those where the leak was placed far away from the attachment point. On average the near leak values were higher than the far leak values by 0 .002

- 0 .003 ” . This w as outside of the margin of error of the EELD was considered a definitive test

influence.

A plausible explanation for this difference was due to the way the EELD and similar devices

compute the leak values. For the EELD and similar test instruments, the effective leak values are

c alculated via onboard pressure and flow sensors. Normally they are calibrated to provide an acc urate reading at the instrument or attachment hose. When the instrument is placed on a test vehicle some pressure drop is always pr esent as long as there is flow through the evaporative system and attaching lines. It is conceivable that the pressure drop present in the evaporative system is greater when the leak location is farther away from the test insertion point. In the data obt ained in NVFEL testing, leak locations farther away from the test point were reported as 0 .002

- 0 .003” smaller than those that were implanted closer to the test point. Based on this testing it may be advisable to consider multiple test points as part of the requirement to show compliance with the requirements 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.019

0.02

0 1 2 3 4 5 6 7 8Indicated Orifice Size



## Test Point Vehicle Inclination Effects (5 ° cant)
0.020" Implanted Leak

5 deg Front

5 deg Left

5 deg Rear

5 deg Right21 Figure 15

– EELD readings for Various Leak Locations

VII. Conclusions

This report is the summary of several months of work of NVFEL testing a nd test procedure development. Pressure leak test equipment was both constructed in

- house as well as purchased from outside vendors for testing. Both types of equipment produced good results and correlation when tested against known orifice sizes. In ad dition the in

- house construction of evaporative test equipment gave particularly well placed insight on the governing physical properties and equations necessary to accurately predict leak sizes from flow and pressure measurements of an evaporative emissio ns system.

Several influencing factors affecting the outcome of the l eak t est were investigated. Within tested limits, the test temperature, vehicle inclination, and fill level all displayed minor influences on the overall test readings obtained. The onl y influence that was seen among the factors investigated was the leak location, which cannot be controlled in a typical testing fashion. In this case, existing instruments can under predict the actual leak by a few thousandths of an inch.

The test procedu re was validated against known vehicle types which represented a difference

from the “norm” in evaporative emission system control or construction. In all instances, the test procedure was effective either as is or with minor well understood modifications

.

Based on the work so far, the test procedure is seen as robust and applicable to many different types of vehicles and evaporative emission systems. However, alternative test procedures are allowed as per 40 CFR 1065.10(c) for those systems which cannot be tested under the given procedure or if new fuel evaporative control system or OBD leak detection methods are developed which are not compatible with this methodology. 0.012 0.013 0.014 0.015 0.016 0.017 0.018 0.019

0.02

0 1 2 3 4 5 6 7 8Indicated Orifice Size



## Test Point Leak Location Effects
0.020" Implanted Leak

.020 Purge

.020 Cap22 VIII. References

1. “ SAE Paper 860086, Composition of Vapor Emitted from a Vehicle Gasoline Tank During Refueling, Robert L. Furey and Bernard F. Nagel, 1986

. 2. VOC composition of current motor vehicle fuels and vapors, and collinearity analyses for receptor modeling”, J. Chin, Chemosphere (Oxford). 2012;86:951

- 958.

3. “Automotive Evaporative Emissions Systems”, M. Schager, University of Southern Colorado.

2011

, pp

. 1

- 5.

4. “Chrysler Evaporative Leak Detection Systems”, Dixon Matthew, 2008. Presentations . Paper 7. http://opensiuc.lib.siu.edu/auto_pres/7

.