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.

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.

-Cory

MC wrote:
: Anybody know how for long the electric fuel-pump
: in a fuel-injected Piper-Arrow IV can be
: operated for.?
: indefinitely ? or intermitantly ?
:
: The POH is somewhat vague as it says that the
: electric pump can be turned-off in cruise and
: I haven't spotted a limitation in the POH yet.

: The reason I ask, is that I normally turn it off
: when in mid climb, but on a recent long trek
: I had some adrenalin surges when the engine
: started getting rough.
: The fuel-pressure was low and varying, hence
: causing excessive leaning, thus rough running.
: Turning on the electric pump got the fuel
: pressure back to normal values and 'ops normal'

: After some experimenting in-flight, I determined
: that the the problem only happened when I was
: using the right-tank, which implies that there's
: some obstruction in that fuel line or in the
: fuel selector.

: So., any views on how long the electric fuel
: pump can/should be run for ?

--
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* The prime directive of Linux: *
* - learn what you don't know, *
* - teach what you do. *
* (Just my 20 USm$) *
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