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Gas tank pressure

We have a 2001 Catera, it has been a jewel so far. However, we had this peculiar incident happen: We have stopped to fill the gas tank (ouch!) but the pump would keep clicking off. We barely put in 2/3 gallons and it would take anymore. The tank was down to 1/4 so we would use another 12 - 15 gallons normally. We drove on that thinking it was a faulty pump at the station. We filled it up yesterday with no problems until we noticed gas dripping from under the frame. YOWZA!!! We have a garage and made a precusory inspection to see if it was repairable. We couldn’t find the leak!!! We took the gas tank lid off and there was some pressure there. We decided to take it to the dealer early this a.m. since we have the “extended” warranty. Of course it isn’t leaking now - so what gives?

Your evaporative emission system is going haywire, probably a malfunctioning purge valve (or whatever Cadillac uses for that function). Has your “Check Engine” light come on?

No, we haven’t had any warning signs - yet! Could it be some sort of clogged vent?

Were you trying to fill the gas tank with the engine RUNNING? If you were, that could be the cause of the problem.

When you try to fill up, with the engine running, and the engine computer (PCM) is running a self-diagnostic, it closes the vent valve which prevents fueling. Shut the engine OFF! See Service Bulletin No. 00-06-04-011, dated February 2000 (It’s STILL pertinent).

If the engine wasn’t running during attempted fill up, then, a malfunction kept the vent valve closed. Test and repair of the EVAP system would then be needed. Make sure the dealer is aware of this Service Bulletin No. 00-06-04-011. DON’T assume that they know about it and have read it.

ADDED: As NYBo pointed out, this vent is an INTERNAL vent from one section of the gas tank to another.

Modern cars don’t vent their fuel systems directly to the atmosphere (it’s against the law). But a clog in the lines is possible. But that doesn’t account for the dripping gas. The system has been breached somewhere.