Some good stuff in
there, Al! What is the propane test??
B2
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Al Wick
Sent: Wednesday, May 29, 2013 10:00
AM
To: Rotary motors in aircraft
Subject: [Bulk] [FlyRotary] Re:
Intermittent fuel pressure loss
Hey Bill. A whole bunch of tests you can do without
flying. I'd sure encourage that. Highly unlikely it's a fuel pump unless you
routinely operate them without fuel. As Jeff suggests, fuel is important pump
lubricant, should resist urge to run sys dry.
If you shared pics, it would help. Particularly
gascolator, pump, plumbing.
Since you get consistent good results from turning on
second pump, that points to flow restriction as likely cause. So a good
test would be to undo fitting at engine and pump fuel into bucket. Measure
volume with ruler and stopwatch. Pump 1, pump 2. This will also disprove pump
theory. You could repeat test by disconnecting fuel return line. This is more
severe test as now pump has to achieve 40 psi. Bad pump would not flow much
volume at 40 psi.
Methodically go thru sys looking for debris, kink. Not
just gascolator, but other areas too. It's possible to have gascolator leak
air and lean sys.
For that matter, you may have engine running lean due
to intake leak (other?), 2nd pump adds touch more fuel per injector pulse.
Thus masking true cause. So I'd do the propane test (or other) for intake
leak. Something loosen during flight and allow leak. Poke and push on
components. Review o2 sensor values. By chance do you record these things
during flight? Do you have other data that can prove it was or was not
lean?
Verify each pump has independent grounds, power
supply. Verify sys voltage. Recalibrate fuel pressure sender.
We have natural tendency to say "aha, I bet that's
it". Forgetting that there are some simple tests to prove it. This is
important time to be conservative and methodical.
----- Original Message -----
Sent: Monday,
May 27, 2013 7:09 AM
Subject:
[FlyRotary] Intermittent fuel pressure
loss
Has anyone had an instance of intermittent failure
of the fuel pumps? A
couple of days ago the engine started to
intermittently lose power and
changed tanks. (both tanks were low, about
5 gal in right and 10 or so in
left) The problem stopped so I
thought I had unported the right tank.
Several minutes later it started
again on the left tank and I turned on the
other fuel pump. That
seemed to stop it again. I still suspected that I
had unported the
tanks.
A couple of days later, I took off with about 45 gal and after
about a 30
min flight, the engine lost power again twice. I turned
the other fuel pump
on and the problem stopped.
My fuel system
goes thru a Gascolator then to the two pumps, then to a
fuel
filter. I assume that the Gascolator or the fuel filter could
be getting
clogged, but I don't think that the other pump would bring the
pressure back
if that were the case. I only have about 70 flight
hours on the pump and
maybe about 100 hours total including ground
runs.
Also on the flight back, I had both pumps on and showing 40 lbs
of pressure.
I then turned the secondary pump off and the pressure held
at 40 lbs. This
strikes me that it is an intermittent pump
failure. I plan to clean the
Gascolator, replace the fuel filter,
and replace the pump.
Any thoughts, suggestions, experiences?
My wife was with me on the last incident and I don't think she is
interested
in trying to join Ed's glider club!
Bill
B
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