Fuel tank pressure

[blisted]

What provides the air pressure in the fuel tank that gives you the pressure release when opening the gas tank?

I've not had a hissing sound in years and suspect that a pump is broken or my patch job on the filler neck is leaking.

 

[pocket-rocket]

I only hear it in the summer time, so I figured it was the air expanding in the tank when it isn't full.

 

[Bryan22]

i don't think the tank is supposed to be pressurized in these. i've never heard a hiss from either my 92 or 94.

 

[Beanmachine7000]

i don't think the tank is supposed to be pressurized in these. i've never heard a hiss from either my 92 or 94.

Me either... The tank on my Camaro does it though...

 

[shadetree]

On EFI systems, the fuel system is sealed and maintains about 1psi of pressure in the tank. You will feel the release when you remove the cap, especially after you have been driving for a while. The cap has a valve to maintain this pressure. Heat also causes expansion which adds pressure.;shady

 

[greaseyfingers]

on my 87 ranger 4x4, 2.9, I've often wondered why there has never been any pressure build up in the gas tank, when I take off the gas cap, even after replacing the old gas cap with a new one, it still doesn't build up any pressure, whatsoever..

is it important for the fuel system to build up and maintain this 1psi of pressure in the tank that you mentioned..

can a fuel system that doesn't build up any pressure, in the tank, cause any engine performance issues..

On EFI systems, the fuel system is sealed and maintains about 1psi of pressure in the tank. You will feel the release when you remove the cap, especially after you have been driving for a while. The cap has a valve to maintain this pressure. Heat also causes expansion which adds pressure.;shady