p.1 

OAR Box 1147 

Prepped by Ollie Stewart 

Document Number: 

157) IV-E-30 

Docket Number: 

A-87-11 

Printed 4/22/2008 2:42:56 PM Sheet 157 of 242 
_-» . sft «5f 

USBJ 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

ANN ARBOR. MICHIGAN 48105 

P.2 

MAR 9(988 

OFFICE OF 

AIR ANO RADIATION 

MEMORANDUM 

SUBJECT: 

FROM: 

Contact With GM Concerning Video Tape of Onboard 

Test Fire 

John F. Anderson, Senior Project Manager 

Standards Development and Support Branch y 

TO: 

THRU: 

Docket A-87-11 

Chester J. Frknce, Chief 

Standards Development an ranch 

On February 26, 1988 I spoke with Mr. Jim Pasek of GM and 

Mr. Robert Lang of Failure Analysis Associates (FAA) concerning 

the test which FAA had performed for GM evaluating the 

possibility of underhood fires from damaged refueling systems. 

FAA had apparently determined that a fire could be started from 

a disconnected refueling vent line when re-routed and placed 

next to a defective spark plug wire capable of producing a 

spark upon vehicle startup. 

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 burn for the 

approximately 6 seconds of filming. In addition, the hose 

itself began to burn almost immediately. 

I had contacted GM to ask how it was that vapors appeared 

to continue to flow from the hose even though the refueling 
P.3 

event had ended and the vapor check valve was closed. Mr. 

Lang, who;:was the engineer at FAA' responsible for the tests, 

first assured me that the vehicle was not being refueled during 

the engine start sequence. He then suggested that the vapors 

flowing in the line during the refueling had sufficient inertia 

so as to continue to flow while the engine was being started. 

He also stated* that the combustion process would create a 

vacuum at the end of the hose and draw the vapors out of the 

line. I found neither of these answers satisfactory because of 

the fact that the vapor cut valve on the other end of the line 

fiad been closed since the end of the refueling operation. Mr. 

Pasek then suggested that perhaps the evaporative vent orifice 

was venting residual tank pressure into the hose, since the 

liquid seal would prevent full tank depressurization 

immediately. 

This explanation seems improbable. 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. However, on 

the assumption that this were a possible mechanism, it is 

apparent that much higher vapor flow rates could occur from 

current fuel tank vent lines during periods of vehicle 

operation as fuel tank temperatures increased. The flow would 

be higher because the tank pressures would be much higher. The 

liquid seal system produces tank pressures of at most a few 

inches of water', while pressures in operating fuel tanks can be 

in the 20 to 40 inch range. Thus, the hazard from such a 

defect mode would appear to be greater with current vehicles 

than from refueling system additions. 

GM did not agree that evaporative vent vapors could be 

ignited. Mr. Lang argued that the vapor flow would never be 

sufficient to produce a combustible mixture, although he agreed 

that a flammability zone had to exist somewhere between the 

inside of the end of the hose and the ambient air. While being 

unable to explain this discrepancy, Mr. Lang maintained that 

evaporative emissions would not reach a combustible state 

during such venting. He also argued that it would take a large 

pool of residual vapors, such as would exist following 

refueling, to initially ignite the vapors or that air flow 

under the hood while driving would blow the vapors away before 

they could ignite. However, he also agreed that a small flow 

of butane as found in many cigarette lighters was easy to 

ignite with a small spark. 

Our discussion was ended at this point because Mr. Pasek 

indicated that he had to leave for a meeting. Mr. Pasek also 

declined to submit a written explanation of how GM believed the 

vapor flow from the hose was sustained.