Maybe I'm missing something, but why not a mechanical pump with a parallel
bypass containing a one way valve the electric pump located upstream from both
the
mechanical pump and valve?
That way the electric just bypasses the mechanical pump and the mechanical pump
won't pump back to the tank(s).
"I did a little checking and you can't push fuel through the VW mechanical
pump
so a backup system would entail, at minimum, a couple check valves and
an electric pump...a bit more complicated that I care to make it."
