Rey, the best thing to do is to drop the tank and to renew all of the
seals and hoses.  That way you also get to inspect the top of the tank
to be sure it is not rusted out.  The bottom of the tanks always look
fine, but the tops can get rusty from junk sitting up there for years.
The plastic cross over pipe can break on one side and you can feel on
top of the to see if that has happened.  However to replace it the best
way is to drop the tank.  The other thing that can happen is that the
rubber hoses on the top of the tank can become dry rotten and brittle
with age and crack.  These can leak like crazy too.  Again the best
thing is to drop the tank, replace all of these.  We have a kit that has
all of the hoses and seals in kit form for $54 without the plastic
crossover pipe.  If you need that pipe let me know and we can get it for
you as well.  We have brand new gas tanks in stock as well.  I have a
write up on my website about how to remove and replace the gas tank.
Take a look.  It is not that bad.  The worst part is draining the gas.
http://www.vanagain.com/gastank1.htm
Let me know if I can help you further,

Rey Wood wrote:
> Hi All,
>            Smelled gas and on looking under the van saw fuel dripping down
> from the back of the tank. 1984 van with original tank which still looks
> perfect underneath and all around & top that I can see. Vent line
> connections are good. Rust perhaps? Anyway of checking short of dropping tank?
>
> Rey
>
>