Gas cap Pressure
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Joined: Jul 2009
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Gas cap Pressure
Help, I have a p0440 check engine code. I was wondering if my gas cap should have pressure build up when I take it off. Mine does not. I'm trying to narrow down the problem. I have already replaced all the hoses to evap systems.
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Joined: Jun 2005
Posts: 14,228
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From: Riverton, UT
The system CAN have pressure but after the purge valve opens the vapor is burned so there would be no pressure. So to go directly off a no pressure instance one cannot tell if it is working. I would just replace the gas cap with one that is NOT vented.