It was the guage!

[Dave]

After the problem stopped being intermittent, and the failure sayed
with is for a while, we got a chance to nail this down, with an extra
tank sending unit to test it with..

Surprising enough, when the guage failed, the resistance was
still about the same as when it was working normally. I suspect a
short in one of the coils that operate the needle, that ocourred when
the guage heated up with operation.

Finally!

GRRRRRRRRRRRRRRRRR !!!


Dave