Vacuum In Fuel Tank

[Scooby]

I'm getting a vacuum build up in my tank - it's obviously able to vent to some extent because occasionally it sounds like someone farting inside the tank. Best way I can decribe it.

The noise stops when I release the filler cap, with an accompanying big rush of air. Just wondering if anyone has had this issue before?

Cheers

[Godzilla32]

The fuel vapours vent through the charcoal canister. A line runs from your tank to the canister which is in the engine bay. At a guess id say there is a blockage somewhere along the line or the one way check valve in the vapour purge line near the tank is stuck closed. Also make sure the cap isnt supposed to be letting air in as the fuel is used up..

[skybarge]

haha i think that's normal, i like the way you describe it as a fart

I get it all the time here in NZ, basically the fuel goes in cold, the day gets warmer and it pressurised the tank, if i open it then, it'll try to blow the cap off into my hand

but if it goes cold overnight and frosts, it does the same thing you are describing, although I've removed and blocked both my carbon canisters off. because after something like 80000k they are useless anyway and we have no EPA here in NZ....yet.

[Trust33]

No epa..

Fek. That be good when you are trying to get the car passed for rego and you want all of the power mods under the sun to stay on.

Do you have db/noise pollution in effect over there?

[kiwi32]

We do have a noise limit but it is realistic. When you mod a car here you have to certify it which is basicly an engineers inspection. Anything goes over here as long as you get it certed, you can then get a warrant and rego.

[Jmaac]

That vaccum is normal, just differential pressure from fuel expanding/contracting with temperature and being pumped from the system by your fuel pump