I was getting this problem ALOT in my impala a while back an di popped the hood and it turned out that the purge canister line attached to my TB was twisted and wasnt getting flow? i guess...I straightened it up and i was allowed to refuel again. Then a month ago i switched to a gen v and my gen v to n * adapter didnt have the nipple on the front so i left it unhooked and the car didnt let me fill up. So my guess is that purge canister lien that attaches to the small brass nipple on the front of your tb near the front valve cover.