P.1 

OAR Box 1830 

Prepped by Ollie Stewart 

Document Number: 

188) IV-C-155 

Docket Number: 

A-87-11 

Printed 11/13/2008 7:21:01 AM Sheet 188 of 232 
> A vi UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

PJ_ 

Pl-<d7-)\ 

ANN ARBOR. MICHIGAN 48105 

,-r-« -r mon OFFICE OF 

FEB 7 I90y AIR AND RADIATION 

Mr. James E. Pasek, Manager cPc°i?& 

Automotive Emission Control ^^v ^ 

Environmental Activities Staff ^o^f-c-^' 

General Motors Corporation £^MV .<$£> 

General Motors Technical Center ^<o riC)&S 

30400 Mound Road a$& ,v^\.^\ 

Warren, MI 48090-9015 G ^ cVy:'.'.--

Dear Mr. Pasek: 

This is in response to your recent letter of January 11, 

1989, concerning the performance of refueling controls. In 

your letter you raised some questions which I will respond to 

below. However, since your letter was in response to my 

earlier correspondence of December 14, 1988, I must raise 

several other matters first. These concern specific requests 

in my December 14, 1988 letter which you didn't address in your 

response. 

First, I made two specific requests for clarification of 

earlier information which GM had supplied to EPA. These were 

for an explanation of an apparent inconsistency in your fill 

test results concerning the occurrence of spitback from your 

system and for a description of the "functional checks" which 

GM performed to verify proper performance of your test vent 

valve. Both of these items deal with key questions in the 

hardware evaluations which GM has performed. I would therefore 

appreciate your response to those requests, which were 

described more completely in my previous letter. 

I also reiterated EPA's request for copies of 19 specific 

General Motors Uniform Test Specifications (GMUTS) related to 

testing of fuel and evaporative systems. As I noted, we are 

aware that your staff had collected copies of the requested 

documents, but that GM had decided to withhold them from EPA. 

Once again, I request copies of these documents. 
P.3 

-2-

Turning to your current letter, you first proposed an 

update on our activities related to refueling control hardware 

since April, 1988. As it relates to General Motors' fuel tank 

systems, we have done no new work beyond that already 

reported. We have applied similar components to a Ford Taurus 

fuel tank, and this has also been documented in the docket. 

That system used a larger canister and involved evaluations of 

improved rollover/vent valves, but neither of these changes 

represent significant conceptual departures from what was done 

to the GM fuel tank. We would be glad to show you these 

components if you desire, since I understand, that as a result 

of Mr. Stempel's December 13, 1988 meeting with Administrator 

Thomas, that GM is preparing a comprehensive briefing for us on 

your technical and safety concerns, we will plan to bring these 

components with us at the time of that presentation. Also as 

part of your briefing, EPA would appreciate an update on your 

onboard hardware evaluation. 

I appreciate your support for our proposal to control fuel 

RVP to 9.0 psi. It appears, however, that some of my 

statements about running losses in that context may have been 

somewhat confusing. I indicated that, when comparing your 

estimates of increased vapor generation from unpressurized fuel 

tanks to those of Ford, that the numbers you found for 9 RVP 

fuel were not excessive given the rarity of the conditions 

involved. I was attempting to indicate that conditions of 

significantly increased vapor generation rates, if sufficiently 

rare, need not cause running loss emissions from the vehicle 

since the canister will be able to contain excess vapors 

periodically for subsequent purging under more favorable 

conditions. Our running loss measurement data indicate that 

some vehicles with non-pressurized tanks are already able to 

contain tank vapors at ambient temperatures up to 95° F. 

Although you have not given us full details on the conditions 

leading to your running loss data, we do know that they 

included ambient temperatures above 100°F, exceeding the 90th 

percentile upper limit value of 96°F for class C volatility 

areas, and extended mountain driving, which would greatly 

increase fuel tank temperature rise above ambient. While we 

are indeed concerned about the control of running losses for 

extreme or near worst case conditions, there are likely to 

always be some extreme cases where it becomes essentially 

impossible to contain all generated vapors. In a well designed 

system, these conditions would not produce direct vapor 

emissions, but would eventually overload the canister, leading 

to indirect release of some emissions from the canister. 
P.4 

-3-

We still believe there, is cause for concern about safety 

risks associated with operating with significant fuel tank 

pressurization. You indicated that operating with pressures up 

to about 40 inches of water would be helpful. Such pressures, 

if not properly contained, could cause large amounts of fuel to 

be ejected upon removing the fuel cap. The experiences of Ford 

with fuel expulsion from ambulance fuel tanks is a clear 

example of this risk. Thus, we continue to believe that 

significant fuel tank pressurization is undesirable. 

Lastly, you asked for information on' what refueling 

conditions, in terms of amount of fill and nozzle clickoffs, 

manufacturers would be required to control. The requirement 

which we have proposed is for at least an 85 percent fueling 

from 10 percent full to 95 percent full, utilizing automatic 

shutoff. This requirement is easily met without the use of 

multiple clickoffs. We would also expect that a well designed 

system would significantly control emissions during topping off 

operations. Even though we disagree on the performance of 

simplified hardware designs, both our testing and yours have 

confirmed this to be the case for prototype refueling control 

systems. Our partial fill tests demonstrated 95 percent or 

greater control during fills from 90 percent full, including 

topoffs. 

I believe this information responds to the questions in 

your January 11, 1989 letter. We look forward to your response 

to the open issues mentioned above and to the upcoming 

technical briefing from GM staff. 

jerely, 

Ches/ter^J. France, Chief 

Standards Development and Support Branch 

cc: Docket A-87-11 

6744W