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Old May 7th 07, 03:00 PM posted to rec.aviation.owning
Jim Burns[_2_]
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Posts: 257
Default Fuel servo output problem (long)

PA32R-300 Lance with factory fresh Lycoming OH IO540-K. After installing a
JPI 800, with fuel flow transducer, the factory Piper and the JPI fuel flow
only indicate 5-6gph fuel flow with the electric boost pump rather than the
normal 10gph during normal start procedures. The engine driven pump
produces the same results after starting the engine and boost pump off. If
you let the airplane sit for 20-30 minutes, an initial 12gph will indicate
on both gauges with the boost pump only, but it drifts down to 5-6gph within
a couple seconds. No greater flow indications are obtained while running
the engine, even up to 1500rpms, full rich mixture.

Idle is rough, engine wants to cut out unless you jockey the throttle.

So with throttle full open and mixture full rich we did the following:
Pulled the output line from the boost pump, volume and pressure like a
firehose. Same thing coming out of the JPI transducer, same going into the
Bendix/Precision RSA 10ED1 fuel servo. Pulled the servo's screen, found
only a couple small magnetic metal slivers. Flushed the screen cavity,
again huge flow and pressure. Reinstalled screen. Pulled the metered fuel
output hose feeding the fuel divider at the fuel divider... no pressure...
BARLEY any fuel! Completely removed the factory new metered output hose
from the servo, inspected, blew air through it with compressor, no foreign
debris or blockages.

Flowed fuel through servo, without the output hose on servo, no pressure and
barely any fuel moving through servo.

We've got huge flow and pressure entering the servo but next to nothing
coming out. Piper fuel flow gauge was just overhauled and calibrated, only
required changing a control arm in the gauge. JPI transducer was installed
according to all JPI documents including factory trouble shooting tips and
trick. Piper and JPI agree during every test that fuel flow is only 5-6gph.
We even removed the fuel line with the JPI transducer, installed the
original factory fuel line, same result, no pressure, not much flow, Piper
gauge indicates 5-6gph.

Fuel flow coming out the individual injector lines is anemic. No line shows
adequate pressure or volume.

The airplane has been sitting inop for 3-4 weeks while this and other work
was being done. Could the ball valve which meters the servo's output be
stuck limiting the output? Any other ideas? The servo should be covered by
warranty through Lycoming if approved by Precision.

Jim