When i fuel/gas up i take my gas cap off and there is a ton of pressure built up in there but it werid i cant tell if its sucking air in or blowing it out. I know the caps are vented but just got my inpection done and he put my cap on a tester deal and it passed. So just woundering if any one has have this prob or if i just need to replace my cap.

 

Mine does the same thing, never really worried about it.

 

OK cool i just thought it was weird because the caps are vented thanks

 

It's sucking in because of when you're burning fuel the pump builds pressure inside the tank, and will actually cause the bottom of the tank to compress when you remove the gas cap it releases pressure hints the sound you hear, and the gas caps are vented yes but it doesnt do crap.