after replacing just about every piece of my gas tank/fuel line system, and
still having gas puke out the filler hole and all over the side of the van when
i topped the tank off, i realized the filler neck was the culprit.  i
remember most of the folks who have this problem have earlier vans..  mine is a 84.
somewhere after 86 or so (or maybe later?), the filler neck design changed,
and a piece w/ a float ball was added to the end of the filler neck, where it
meets the tank. my '84 just had a curved end where it meets the tank - no float
ball. so basically when i filled the tank up - there was nothing preventing
the gas brom backwashing up the filler neck and out the filler hole and all
over the side of the van.   i remember i never had this problem on my '89 carat..
    so...  i took the '84 filler neck off, and installed one from a '90
vanagon - that has the float ball..    VIOLA!!!   problem solved!.
i suggest everyone who is having this problem with their earlier vanagons,
install a filler neck off a late model vanagon with the float ball piece at the
end.
fyi, i have 2 of these for sale..
chris