(Ben Jackson) wrote in news:Fsauc.11099$IB.10366@attbi_s04:

Anybody know how for long the electric fuel-pump
in a fuel-injected Piper-Arrow IV can be
operated for.?
indefinitely ? or intermitantly ?

All I know for sure is that the one in my plane (PA-24 Comanche) is
shockingly expensive so I only have it on for takeoff, tank changes,
approaches and landing.

Yes, but the Comanche has an additional issue. It's boost pump is in
parallel with the engine driven one. So if you run it, fuel doesn't
necessarily continue to flow through the main pump. Where the main pump
is located on the Comanche is a high-heat area. Without the fuel to
cool it, the fuel can vaporize. Then when you turn off the boost pump
the main pump doesn't take over and, a moment later, the engine quits.
Gets your attention.

You can get the engine back with the boost pump. You can then get the
main pump back online by "pulsing" the boost pump on and off repeatedly
until the engine continues to run with the boost pump off. Or so says
the Comanche Society film on the matter... I haven't tried it in
practice.