Hard to Start After Fillup +CEL

[ABC_Driving_School]

I have an '07 NB with about 108K miles. The CEL has been on for a while and I had it scanned a few months ago and while I can't remember the exact code, it had to do with the fuel vent valve.

There don't seem to be any driveability problems, but it is doing a couple of weird things. The first is that after filling the gas tank, the car is very hard to start. I have to hold the gas pedal almost all the way to the floor while cranking it, and then let off as soon as it fires. But this ONLY happens after filling up. If I just remove and replace the gas cap without actually adding any gas, it will start right up.

The second weird thing is a distinct thumping noise coming from under the car while the engine is warming up. It sounds as is someone is tapping on the bottom of the car with a rubber mallet.

My (albeit limited) logic skills are telling me the hard-start-after-a-fillup is related to the fuel vent valve and maybe the thumping sound is the plastic fuel tank flexing.

I am going to have it scanned again to get the exact code. Assuming the fuel vent valve is the problem, is there a DIY article on how to replace it? I spent about an hour searching this and other forums with no results.

Does anybody have any advice to offer?

[turbokid]

Post the CEL code and I'll look it up in my Bentleys. I looked for "fuel vent valve" and came up empty so it's called something else.

The fuel tank is pressurized with a small pump which checks the integrity of the closed duel system. Removing the gas cap relieves the pressure. It couldbe the pump is not cutting off puting too much pressure into the system. Without the CEL code this is a wild guess.