96 Cavalier 2.2
Whenever I drive around for a while, if I take off the gas cap there is a ton of built up air pressure.
I already replaced the gas cap but it still does it. What else could be causing this build up of air pressure in the tank?
Thx
The fuel system itself does it.. it's supposed to do that. That's why you installed a pressurized gas cap, in fact.. if you don't have pressure in the tank, you'll get a check engine light as the pressure sensor mounted on the top of the fuel pump assembly (in the tank) won't pick anything up.. ie, if you have a defective gas tank.
It's normal
...j
I thought the EECS purged the vapors back into the intake.
It's the Evaporative Canister Purge Solenoid Valve (ECPSV if you will
) that allows the vapors to flow from the EVAP canister into the engine. The pressure sensor mounted on the fuel pump will pick up differences in gas tank pressure as the tank level goes down. If the signal stays in one spot for too long referenced to the other sensors, it will throw a code and check engine light. Since the OP didn't mention the light, I'm assuming all is kosher.
Now, if there IS a check engine light... and you scan a P0440 code, combined with a P0462 or P0463 code (can't remember which is high voltage or low voltage... but one of them will come up) then you DO have a problem with the pressure being too high. Unless there's a code stored, I really wouldn't worry about it... but if you are really concerned, any GM dealer or reputable mechanic should be able to test the EVAP system to ensure the charcoal canister is loading properly. Could be yours is on the way out... hard to say without actually seeing it in person.
My old 94 Geo Metro used to really build up tank pressure... damn thing would go "WWWWOOOOOOOOOOOOOOSSSSSSSSSSSSSH" when I opened the gas cap
but it was fine...
...j
Got no light but when I took the cap off today after it was sitting for almost a full day, air came whooshing out of it for almost 5 seconds. There seems to be a really excessive amount of pressure in there.
I've had over 30 vehicles and none have ever been this bad.
