Armchair mechanic opinion - gas lines are being heated to/from fuel rail via engine bay, causes vaporization which then gets deposited in the tank on the return line. Try heat wrap on the fuel lines? Or heat shield around exhaust/engine block?
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On Jul 13, 2023, at 14:43, Jerome B Dwight <jeromebdwight@...> wrote:
That sounds dangerous to me. A friend was incinerated when he carried gas in his car on a hot day. With the right fuel/air mixture the dome light can ignite the fumes.
On Jul 13, 2023, at 4:57 PM, Michael Diehr <md03@...> wrote:
?I repeated my usual drive which triggers the problem: up the 395 through Bishop (roughly 4000' elevation) then up the steep climb towards Mammoth. (7000' elevation). It's a roughly 3000' elevation gain in about 30 miles. Temperatures were hot but not exceptional (95F or so).
As I got above 6000' I noticed gas fumes while driving. Pulled over, turned off the engine. Got out of the van, could not locate the source but it seemed to be near the tank (not in the engine compartment, not the tailpipe).
I opened the gas cap and vented the tank until it stopped outgassing. It was a tremendous amount of gas. Once all pressure was gone, I continued on to my destination which is over 7500'.
I was no longer smelling fumes at that level, but after I stopped, I did a test. The engine was still running.
I opened the gas cap. Again, there was tons of gas escaping, as well as some drops of liquid gasoline.
- with an IR thermometer, I measured the temperatures of the gas tank exterior and gas coming out of the tank: about 120F. Warm, but really not hot enough to account for this great volume of vapor.
Here's where it gets interesting:
- I stopped the engine, and the vapor quickly stopped.
- I started the engine again, and within seconds, the vapor is flowing out of the gas tank again.
- I stopped the engine, and the vapor stops.
This feels like an important clue: why did stopping the engine stop the vapor?
Mike
