97 Bravada Gas Cap Pressure

Hey all, my 1997 Bravada makes a whoosh sound and releases air when I take off the gas cap to fill the tank. Is this normal? I thought it was the gas cap so I replaced it and it still does it. I replaced the tank, the fuel pump because they were bad and it still does it. Is this normal?

Any pressure build up in the fuel tank is vented through the evaporative canister/system.
I'd look for a pinched hose near the fuel tank.

Any pressure build up in the fuel tank is vented through the evaporative canister/system.
I'd look for a pinched hose near the fuel tank.

I will take a look this week end. Thanks. I know the lines going to the fuel pump aren't bent or broken, I took a good look at them when the tank was down. Do you think the evap canister could be bad? Every once in a while I get an evap code. PO440

I did some checking and according to the Fixya site, a P0440 could be caused by a pinched line.

Good job Chris, a pinched line could do it. P0440 covers the entire EVAP system. It's a very "general" DTC and doesn't specify if the problem is mechanical or electrical. Check the purge canister vent solenoid. Can't recall exactly where it is on yours, but the canister is behind the driver rear wheel. Follow the large hose, it goes right to the vent solenoid. Unplug and remove the solenoid. The fitting that the large hose connects to should be unrestricted, (you should be able to blow through it easily). If the solenoid is stuck closed, pressure can build in the tank.

http://www.amazon.com/ACDelco-214-633-Vapor-Canister-Purge/dp/B000C9GLIO

Thanks OM!

Thanks for the replies guys.
I was under the Bravada this week end and the large hose is very dry and cracked. It looked like it had collapsed in one of the bends going to the purge container. I straighten out the hose and drove it about 60 miles and let it set over night and gassed it up the next day. When I took the cap off there was no pressure or hiss. So maybe that is the pressure issue. I am hoping that is causing my PO 440 code at times also.
Thanks for the link to the part OM!!! I think I may just replace the whole system when I replace the hose.

Glad we could help. Keep us posted. Thanks for posting back with the "fix".