Posted by Joe Divito (IP: 207.239.0.112) on November 03, 1999 at 18:08:29:
In Reply to: Gas tank troubles... posted by Chris on November 02, 1999 at 17:26:33:
I had the same problem, usually on hot summer days, when I first got my Comet. Changing gas caps solved the problem. There's a pressure relief valve built into the gas cap on most Mavericks/Comets built when the EPA required special vapor recovery devices. The relief valve is supposed to open when pressure in the gas tank becomes too great (kind of like a radiator cap).
Also check that the vapor recovery line is not kinked or disconnected (and capped off). You should see a second rubber line running forward from the tank (should be somewhere at the top of the tank) towards the engine compartment. The hose is supposed to carry gas vapors to a special charcoal filled canister, which holds them until you start the car. Engine vaccuum (there's a second hose leading from the canister to the air cleaner) draws the vapors out of the canister, where they're burned.
If that hose is pinched off (or disconnected by a well meaning, but uninformed mechanic), you'll have a problem, since the gas caps are not supposed to allow gas vapors to escape unless the pressure becomes too great. If that relief valve sticks, I suspect the pressure may become great enough to cause the gas to percolate back up the filler tube.
Hope that helps,
Joe