Every time i take off my gas cap to fill up the tank it sounds like i'm opening a bottle of coke, like it's releasing air that was built up in my tank. What is happening to cause this. Is it a problem, if so how do i fix it?

 

gas is volatile, which means it becomes a vapor very quickly. This creates a higher pressure in the tank, so you hear it escaping.

 

i don't know for sure--so don't bite my head off for saying the wrong thing but here's a guess....
It allows the tank to pressurize to assist in pumping the gas throught the fuel lines--other wise i believe they would have put a vent on the gas cap!!!

correct me if I'm wrong!!!

 

ok, i just never heard it in any other cars, but i've heard it before in the canister we keep the gas for our lawnmower so i figured that was what it was. Thanks.

 

i was wondering the samething every time i fill up after driving for a little while... it doesn't happen when the car is first started up in the day. That's the only thing i could come up with for now!!!

 

The fuel pump is builds up the fuel SYSTEM pressure to, what, 30 psi (someone out there care to correct this if I'm wrong on the psi). at the injectors. From the injector rail, there is a return line back to the fuel tank sending the unused fuel (and the pressure behind it) back to the tank.

This is most noticable when you have a near empty fuel tank as the volumn of air is it's highest (air where fuel used to be).

How's that for an answer?

 

sounds more detailed than mine!!!!

 

 

if you have an aftermarket fuel pump w/ a consant 12v that will give you that all the time....

I have a nippodenso high flow pump supports over 500hp. and 12v direct.

I get a lot of pressure in my tank especially when its nearer to empty than full. I don't think its to big of deal. I've never had a problem with it....Im sure the fuel tank and lines can support the amount of pressure thats holding in.

--

matt