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my engine continues to baffle me and
everyone else on the airport. I would send it to a mechanic, but I've
spoken with all of them and they have no ideas either. it continues to
look like fuel starvation, but no gauges support this theory. it runs at
2150rpm, burning 11.5-12.3 gals per hr, 3 lbs fuel pressure, for about 2 minutes
then stumbles(and will die unless I reduce the throttle to 1500rpm. )the
stumbling occurs when cht's are hitting 375 - 410. continued running
at 1500 allows the cht's to climb, so I have to shut things down. the same
behavior occurred when I flew the plane the first two times (until I realized I
could duplicate the problem on the ground) I have a new carb(ma4spa) and 4
rebuilt cyls (on which I am attempting to set the rings, unfortunately) if
I run the engine at less than full rich the engine won't stumble before temps
hit 400+ and I have to pull power.
I bypassed my fuel filters with no
difference. I installed new filters that have a core of little brass balls
stuck together and seemingly much better flow than the other filter(no
angles either, just straight flow)
I cleaned and backflushed the fuel
pickups and vents, ran with the gas caps off(no diff). my fuel flow is not
changing(until it sputters back to 1500rpm), so my idea that the carb bowl was
slowly not being refilled doesn't show up. the same problem existed before
I had the cyls rebuilt and welded, so I doubt that stuck valves/weak
springs are to blame. also, that would show problems from the start,
not a few minutes later.
everyone wants to blame the electronic
ig. switching between mag and elec. during the first minute shows no
diff. switching after it starts to falter shows no diff. pulling
back to 1500rpm after falter shows no diff. I can't believe I have a
spark or timing problem because there are no times when one works and the other
doesn't. my slick mag is brand new also. I haven't tried new plugs
yet, the current ones are new, although I've heard many stories of bad new plugs
(hey, what do you want for $20?)
my 1" dia. cheapy van's fuel pressure
meter is now showing 3 lbs. I removed the pressure regulator. in the
past it used to show 8lbs pressure (hence I installed the regulator)and my carb
showed signs of leakage which is one reason I replaced it. I have no idea
why it shows only 3 lbs now. I tried plumbing the carb directly from a gas
can. I forgot to switch the fuel line off and shot fuel clear out on the
wing when the engine started. I would guess that the mech. fuel pump is
working correctly. the facet elec pump will pump about 1 gallon in 2
minutes when pumping into a gas can thru the mechanical pump. it makes no
diff. if I run the facet or not. I have bypassed the mech. pump and run
just with the facet, no diff., in fact, when I shut off the facet the engine
still runs until the bowl burns down, maybe 30 sec.?
it is hard to believe that both the auto
plugs and aero plugs are simultaneously failing due to heat. I could fly
the plane at less than full rich to see how long it would fly I suppose, but
that seems unnecessarily risky. I've had two "lucky" flights so
far.
I checked for induction leaks(pressurized
and soap solution) and found nothing.
I am out of
ideas. this problem is just kicking my butt. hopefully one of you
guys will spark an new idea or theory for me.
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