With any luck this link will go to several photos of the inside of a
gas tank from a 1984 Vanagon.
http://s197.photobucket.com/albums/aa190/becida/84%20Fuel%20tank/

With around 4 gal left in the tank the van ran like it was out of
fuel, more gas fixed the problem. The fuel pump made a lot of noise,
the PO had changed the pump to fix the noise but the new one made the
same noise.
After a thread about this on the list I ordered a tank and changed
it. Having a 'bad' fuel tank in front of me and really wondering
about the 'screen' that prevented my using the last 4 gallons I
really had to take a look.
After cutting the tank in half I don't see a problem. No screen to
clog up, the hoses from the sump were not blocked.
I can see no reason why I couldn't use the rest of that fuel, but it
was running out of gas with 4 gallons left.

Anyway here are some photos. (The pump does run quiet now)

Rob
becida@comcast.net