If your van has spent much time within the Rust Belt, the tank may be rusted
through in the area of the tunnel (perhaps valley is a better term) on its
topside.  Slush saturated with road salt tends to become packed in there.  If
you are anywhere near SW PA, I have a rust-free tank should you need it.

If you want to lower the fuel level before you move the van, the Digijet
system, at least, has a pressure test point in the fuel supply line in the
engine compartment.  This is in the form of an inline Tee with a plugged
center branch.  This fitting is sized such that a small diameter hose can be
slipped over its center leg in order to pump out fuel.  I do not not if the
same test point is in the Digifant system since I have not needed
it.......yet.
Rich