Uh, first of all, you have to see a leak to seal it.
His sounds more like the venerable cross-over tube syndrome leak.
Me in AZ

----- Original Message -----
From: "Jim Felder" <jim.felder@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, February 11, 2010 6:43 PM
Subject: Re: Gas Tank Leak!

I had the same thing happen seven years ago and I stopped in an auto
parts store and got some gas tank putty. No trouble since. It works
even with gas streaming out. I keep it in my tool kit now.

Jim

On Thu, Feb 11, 2010 at 7:18 PM, Rey Wood <boscobelle@live.com> 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
>