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Discussion Starter · #1 ·
I have had this problem or at least i think its a problem when i take my gas cap off it about flys out from the pressure blowing out. I know there is a warning to remove gas cap slowly but when I do and it still dose it. Im just checking with you guys to see if that might be a problem. I have a new gas cap that was bought last year. LMK

Thanks
 

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You should be okay, I would think. When i stop to tank up, I get a hissing coming from my tank. Others will chime in saying they don't hear any hissing. Personally, I am glad I hear it because then I know I have pressure in my gas tank.
 

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It's all good. You should hear hissing from the air pressure, that means your gas cap is providing a good seal and your tank is staying pressurized.
 

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Discussion Starter · #4 ·
I do agree there is suspose to be a little pressure but when i open it i can feel the build up blow past my arm.
 

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I do agree there is suspose to be a little pressure but when i open it i can feel the build up blow past my arm.
That's too much pressure. It sounds as if the tank is not venting as it should. The cannister is purged by the PCM under specif conditions. Sounds as if yours may be malfunctioning.

Check the gas cap.
Get the codes scanned. Even though the check engine light is not on, you may have a code stored.
 

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That's too much pressure.... Check the gas cap.
Why check the cap? It appears to be doing it's job, that it to seal. Excess pressure is not a cap issue as it can not seal too well. :)

"It sounds as if the tank is not venting as it should. The cannister is purged by the PCM under specif conditions. Sounds as if yours may be malfunctioning."

I agree and that is why I don't undertand the cap comment. :)
 

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Discussion Starter · #7 ·
That's too much pressure. It sounds as if the tank is not venting as it should. The cannister is purged by the PCM under specif conditions. Sounds as if yours may be malfunctioning.

Check the gas cap.
Get the codes scanned. Even though the check engine light is not on, you may have a code stored.
well i know its not the cap because its brand new just got a new one yesterday and the problem is still occuring. I have to check the lines to the canister that probably is my problem ill let you uys know when i do it.
 

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Have had the same question about tank pressure since I've owned the car.

If I'm driving for a bit when I remove the cap there's an assload of built up pressure, yet if I just start the car for the day and drive down the block to the station and there's nothing. No CEL and no codes stored.. I believe our EVAP systems are working just as they should, I have never had any other reason to think otherwise. I had replaced the lines to the EVAP purge solenoid on the passenger side of the intake with new, replaced stock cap with a locking one.


Just realized this is an old post.. any updates, Suicide?
 

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My 93 has done this for a long time. It doesn't seem right.
 

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Both my current B-bodies do this despite me replacing the purge valve and checking to make sure the vent line from the tank isn't pinched shut (I couldn't pull a vacuum on it). They only do it when the car's been driving for a long time and the tank is empty, so basically the fuel system has had time to heat the air in the tank. Every other time, there is little pressure in the tank.
 

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So, is this a B-body or a LT1 fuel system thing? Anyone have an LT1 F-body that does the same when removing the fuel cap?
 
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