If so, I just fixed this problem for about $8 on my vanagon.

Everytime I filled up, no matter how slow I went when I knew it was getting
full, when the pump would click, gas would come out ( about a cup full or
more) the filler neck.

I investigated the seals on the expansion tanks along with the white check
valves that push into seals.  One of the check valves was frozen (the new
ones rattle when you shake them) and now when I pump the gas it clicks and
my gas stays in the tank.

If anyone wants the part numbers, let me know.

Adam Puzerewski
81 westy
74 beetle

Vanagon Partsmobiles