Pressure when opening gas cap

[schwarze_crewcab]

After I have been driving for a while and open the fuel cap, I get a woosh of air. I noticed it lloks like this rig has an EVIC system. So, any idea where my problem might be? The cap looked like it may have some sort of vent, but I'm not certain. I would like to fix this, as I wonder if it might help my fuel mileage a bit. Thanks

 

[sewlow]

Could be that the gas cap's vent is S.O.L. Usually when my gas caps have died, the computer throws a code. 'Fuel Evap' or 'Fuel Recirc.', or some such thing.
Try a new one. About $10.00.

 

[Kyle97GMC]

Mine does that too. Does it hurt anything? I had never been too worried about it

 

[sewlow]

I only worry about it once it throws a code.

 

[Kyle97GMC]

I only worry about it once it throws a code.

Ok sweet. I will keep an eye out for that

 

[great white]

Some vacuum on the tank is normal. It's part of the evap system. It makes a "whoosh" sound when you crack open the cap if it's holding just a touch more than most. Most will make a slight and very brief "sssss" sound as you loosen the cap.

 

[glfirefighter144]

Some vacuum on the tank is normal. It's part of the evap system. It makes a "whoosh" sound when you crack open the cap if it's holding just a touch more than most. Most will make a slight and very brief "sssss" sound as you loosen the cap.

i agree, nothing you can do unless it throws a code, other than change the cap, but that ain't guaranteeing the whoosh will go away

 

[///RAGMC]

My 91 does it badly when its hot outside im thinking its a pinched line somewhere

 

[benz88]

My caps under a year old right from GM and it still made the Woosh sound. Its normal.

 

[southern_z71_92]

my camaro did it and i never had any trouble out of it. still got 16 mpg.