Since someone just posted a good pic of our evap lines, I thought I'd start a thread that ties in a few very informative threads (Terry and Matt D) with a very common and annoying CEL. Please post if you have anything to add.
CEL 31 supposedly occurs when the EVAP system sees positive pressure and a membrane ruptures.
A one way check valve is an easy and cheap preventive measure. When you are boosting, which line should have the check valve to avoid the Evap code? A or B or C?
#110733, "RE: CEL 31 Prevention" In response to Reply # 0
Boost pressure will not damage any evap equipment Erik. The only concern was the Rollover valve and proved that its not possible. Like I said before, i have boosted mine to 30psi and never damaged anything. Its been proven, period.
The main key is to keep all the rubber lines in good shape. The rollover valve clearance issue could be fixed with a hammer if you wanted to dent the bottom of your car.
The rubber lines are notorious for developing dry rot cracks, I have seen that many times on both my cars and other people's cars.
Gas cap has been known to fail in the vent.
The rubber diapgram you refer to in the rear of the gas tank is the fuel FILLER NECK. Its a rubber hose just like a radiator hose. You can develop leaks if a clamp fails or the hose dry rots.
#110741, "RE: CEL 31 Prevention" In response to Reply # 1
Originally posted by Star Turbo Talon The rubber diapgram you refer to in the rear of the gas tank is the fuel FILLER NECK.
Terry, I know I'm reiterating here, but to quote Matt from the thread I linked "Well I know for a fact, at least for the turbo guys, that this CEL is caused by a valve right between the gas tank, and the spare tire well , under the car. There is a rubber diaphram inside it, and can tear if it sees boost pressure. In the center of this diaphram, is a plastic pole piece, with sharp edges on it, on the underside of it, and if boost pressure gets in it, can tear the diaphram on those edges."
That doesn't sound like a filler neck, he keeps referring to a diaphram.
I know you disagree strongly with the theory, but considering I have never seen it with my own eyes, I have to go by the evidence:
A)RUBBER diaphram (per Matt), which can be exposed to: B)boost pressure, via the EVAP lines
A+B=potential failure point. A $1.30 one way stop valve seems like a good idea
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