My car has built up pressure in the tank, and I can hardly put the nozzle on the gas pump in it and squeeze and it shuts off, or if I just hold it down it will shut off and shoot out. I recently replaced the fuel filter, and I went to fill it with gas it was fine, but now today it's same as before...any ideas?

 

Your tank does build up pressure when you drive. That is why you always hear that hissing sound when the cap is released. You may want to try to back out the nozzel a tad when fueling.

 

I don't know if it's the diameter of the neck or just a messup on GM's part but what you're talking about is an inhearent(sp) problem with 3rd gens. If the nozzle has one of those springs on it...try backing it about 2 notches in that spring.

Hope I was helpful.

 

Thanks guys, but why did it fuel fine after i changed the fuel filter? just an oddity or does anyone have an explanation?...

 

Thats just a strange coinsidence(sp). 3rd gens have always been wierd like that with filling up.

 

What does it mean if your car doesnt relieve pressure when I release the cap? I noticed my car never makes a hissing sound when I fill it up.

 

Same question. My car used to hiss and now it doesn't. what does it mean.

 

I beat all of you. I have the same problem with my tank building up pressure. It not only will hiss when i take the cap off but on a nice quite night or day i can hear my car make a a noice similuar to a cows moo. I have gotten used to it but its funny to watch people walk by my car when it goes off. The only thing i can think that it is, is the gas tank tank reliveing pressure from somewhere.

 

The charcoal can is supposed to capture those vapors and keep the internal pressure relatively low. Im not real familiar with whats along the lines that lead up to the charcoal can but there is a valve there and I imagine somewhere along the way something is blocked. That sound is the pressure relief valve allowing the fuel vapors to escape.

 

Older cars just havs a vent some where under the car our cars vent at the tbi. vent lines goes from the tank to the charcoal canster with a one way valve. The ECU open the canister to a vacuum port on the tbi and gets sucked in to the motor. If you have too much pressure it will vent into your engine compartment from the canister. No presure means a leak some where. Every once and a while I run across some that have clogged lines. Some even "fart" out past seals.

 

Oh and its not a good Idea to just cut the line and vent it under the car. A 68 impala as an example the vent line runs from the top of the tank inside the trunk by the passenger wheelwell to the top of the fender back under the trunk with a plastic filter made to catch any fuel that might have made its way past all the bends in the line. I bet Hot exhaust and fuel vapor don't go well together.

 

Thanks guys. you've answered a confusing question that ive been scratching my head at for a long time. I will check all that. Thanks.