Originally Posted by
Joe_Black
A couple things could be going on, but they're centralized around the charcoal canister underneath the VX just in front of the fuel tank on the fuel-filler side. There's a solenoid valve and the canister itself that could be at fault. The solenoid could be faulty, failing to switch the vent lines as needed, or the canister could be bad. If you overfill the tank times it could flood the canister. There is also a possibility of a sensor issue or perhaps the associated lines, but the two above are the most common.
In the CD shop manual there is detailed information on the canister and how to troubleshoot the system.