GM Repair Questions? Ask a Mechanic for Answers ASAP
Hello I will help you with your question,
There is a problem with the canister vent valve on your van and it is not opening to the atmosphere when you turn the key off as it is designed to do.
The valve may have an obstruction like a wasp nest or the valve itself may be stuck closed. The default position is open when power is not applied.
The valve is located on the inner frame rail near the fuel tank
Let me know what I can do to help you with this
If the fill hose is falling down to the point that the hose kinks at the bottom this could be the problem with the fuel backing up and if you had the vehicle running and the engine computer picked that moment to run the built in emissions test the valve would have been closed electrically so either of these could be the problem
I would have the filler neck repaired and turn the van off to fuel it then see if you are still having problems