wrote:

Aside from wearing the pump out prematurely, there's nothing significant about
running it for long periods of time. Of course, if you left it on indefinately, you'd
get no indication about one of the pumps failing.

I had a similar experience in my Cherokee 180 on the right tank. About 400'
AGL after takeoff on the right tank, the engine sputtered to a stop. No fuel
pressure, and the boost pump was already on. Switching to the left tank fired it back
up. Took about 3 seconds to diagnose, act on, and get the engine running again, but
felt like 3 hours. I had noticed a drop in fuel pressure at high flow conditions
(full rich takeoff) on the right tank before that time but didn't think much of it.
After that incident, we tore into the fuel system and found a paper wasps' nest in the
right tank fuel line after removing the tank. I'd suggest any discrepancy like that
to be looked into and the problem found.

Yeah.. I'm sure it's an obstruction, but at the moment I'm a lonnnnng way away
from any reasonably equiped repair shop.

Also, just as a data-point. The Cherokee (not sure about the later Arrows)
line has an extremely *marginal* electric boost pump stock. We ended up installing
the Petersen autofuel STC on our plane which requires replacing the stock pump with
two (only one at a time) replacement pumps. Rather than pumping around the engine
pump, they can (individually) pump through it now. Before the upgrade, I never saw
much difference between the pump being on or off. Now, in full-power climbout, I see
5 psi with either boost pump, or about 2 psi when I turn them off. According to
Petersen, the fuel pump swaps were necessary when the stock pump, "failed to meet
miniumum flow requirements." A euphamistic way to say Piper's original design sucked
and wouldn't pass ceritification requirements today.

It may be just my combination of equipment, but with the electric pump on, the
fuel pressure stays fairly stable, but the engine-driven pump has never given
a constant reading, it fluctuates from minimum to about mid range on the gauge.