Why does my gas tank pressurize?

[Msaone]

Working with my sons car 89 rs 305 and we noticed that when opening the gas cap, the tank pressurized. We changed the cap and its still dong it.

What should I check?

[nascarnate326]

I think they are supposed to be that way. My Camaro is pressurized as well.

[1BADAIR]

The caps stopped being vented in the 70's. now they vent to the intake. Is the emission stuff removed? Purge solenoid, canister ect

[WMCCjames]

Your vent line going to the charcoal canister is plugged.

[Msaone]

The caps stopped being vented in the 70's. now they vent to the intake. Is the emission stuff removed? Purge solenoid, canister ect

Good question. Ill have to check. Is it under the hood or in the back quarter panel?

[Msaone]

Your vent line going to the charcoal canister is plugged.

Hope so, someone else suggested the canister is gone.

[bigjon88]

http://moderndaymuscle.com/inc/sdetail/850
I

[Msaone]

http://moderndaymuscle.com/inc/sdetail/850
I

Thats the cap I was looking for. Thanks, That'll save a bunch of time.

[Msaone]

Wonder if I can find that locally?

[hoogiesngrinderz]

FYI vented caps will allow air in, not out. Some pressure is normal.

[Msaone]

FYI vented caps will allow air in, not out. Some pressure is normal.

That's just what the guy at the local auto parts store said.

Forgive all the questions, just getting back in to wrenching here.

[hoogiesngrinderz]

No problem! Check the EVAP system anyway, if it is even there