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OAR Box 1830 

Prepped by Ollie Stewart 

Document Number: 

127) IV-C-93 

Docket Number: 

A-87-11 

Printed 11/13/2008 7:20:58 AM Sheet 12 7 of 232 
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-*' ^ \ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY ^ ^ " i as 

' / 

ANN ARBOR. MICHIGAN 48105 

*•< PRO* * 

MAR I T 1988 

OFFICE OF 

AIR AND RADIATION 

Mr. Samuel A. Leonard, Director 

Automotive Emission Control 

Environmental Activities Staff 

General Motors Corporation 

30400 Mound Road 

Warren, MI 48090-9015 

Dear Mr. Leonard: 

This letter is a followup to conversations my staff have 

had with General Motors concerning one of the video tapes which 

GM submitted as part of its comments on the onboard refueling 

proposal. The tape in question documents tests done for GM by 

Failure Analysis Associates (FAA) evaluating the possibility of 

underhood fires from damaged refueling systems. 

In the. test sequence, the refueling vapor hose was 

disconnected from the refueling canister, which had been 

located under the hood, and re-routed so as to end immediately 

adjacent to a damaged spark plug wire. The vehicle was 

refueled with 15 gallons of fuel, the nozzle was returned to 

the fuel dispenser, and the vehicle subsequently was 

restarted. In a video tape of the hose outlet under the hood, 

the vapor surrounding the end of the hose was seen to ignite 

upon engine engagement. The vapor continued to be emitted and 

burn for the approximately 6 seconds of filming. In addition, 

the hose itself began to burn almost immediately. 

My staff had contacted you to ask how it was that vapors 

appeared to continue to flow from the hose even though the 

refueling event had ended and the vapor check valve was 

closed. You had apparently referred the question to Mr. Jim 

Pasek who, along with Mr. Robert Lang of FAA, contacted us for 

followup discussions. During the discussions, Mr. Pasek and 

Mr. Lang offered several possible explanations for the events 

shown on the video: 

(1) The vapors flowing in the line during the refueling 

had sufficient inertia so as to continue to flow 

while the engine was being started. 
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" (2) The combustion process would create a vacuum at the 

end of the hose and draw the vapors out of the line. 

(3) The evaporative vent orifice was venting residual 

tank pressure into the hose, since the liquid seal 

would prevent full tank depressurization immediately. 

We find none of these answers to be fully satisfactory. 

The first two reasons are inconsistent with the fact that the 

refueling vapor shutoff valve on the other end of the line had 

been closed since the end of the refueling operation. As for 

the third explanation, venting at the high rate seen in the 

video would have equilibrated the tank in a few seconds, most 

likely before the engine start sequence even began. If the 

venting were slow, then it is difficult to understand how the 

large burn rate was sustained. Furthermore, if venting through 

the evaporative vent orifice was capable of releasing such a 

high volume of vapors at the relatively low in-tank pressures 

generated during refueling, then much higher vapor flow rates 

could occur from current fuel tank vent lines during periods of 

vehicle operation as fuel tank temperatures increase. As you 

are undoubtedly aware, fairly high in-tank pressures can occur 

under such conditions, much higher than the liquid seal system 

produces during refueling. Thus, the potential hazard from a 

disconnected vapor line would appear to be greater with current 

vehicles than from refueling control system additions. 

Since the safety of both current and proposed control 

systems is an important concern, I am writing to request a 

further explanation of the vapor release during these tests. 

Please identify possible sources of vapors and mechanisms for 

release from the refueling vent hose in quantities sufficient 

to produce the observed fire. Also, please address the means 

by which the vapor hose itself and the spark plug wires were 

able to ignite almost immediately. Our experience indicates 

that it is normally quite difficult to ignite heavy rubber 

hosing and wiring such as pictured in your system. Finally, 

please describe how the car was conditioned prior to the 

refueling test, and whether the car was driven or standing 

still while the engine was being run. 

Since we are already in the midst of our review of 

comments, and since safety concerns are of paramount 

importance, I request your prompt reply to this matter. I 

would appreciate a response before March 30, 1988. 

.es L. Gray, 

Director / 

Emission Control Technology Division 

cc: Docket A-87-11