Engine Performance problem
1997 GMC C1500 V8 Four Wheel Drive Automatic 58000 miles
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I hear a lot of hissing when I remove the gas cap on my truck. I just replaced all fuel lines (supply,return,vent), fuel tank, complete fuel pump, filter, filler neck, and gas cap.

The truck runs fine, there's no check engine light.

I checked the vapor line to the canister with vaccum/presure pump engine not running. it held both vaccum and pressure.

my concern is that the tank may implode or colapse if its not vented properly.

I don't ever remember any hissing from the tank before. I've owned the truck since it was new.

Thanks

It is normal to have some pressure in the tank and you have stated the check engine light is not on so I would not be concerned. And BTW, the tank is not going to explode. OBDII criteria requires tank leakage monitoring and if there was an issue with the tank or the evaporative emissions, then the check engine light would come on.

What does BTW mean?
I'm worried about the tank Imploding. Or compressing.
Is there a way to test the purge solenoid?
Thanks.

BTW is by the way. The purge solenoid is tested by the system, if it was not working then the check engine light would be on.