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Kevin,
I still would bet on fuel delivery. As it sounds it must
be in the carb itself.
As Walter Kerr suggested, try another carb. Do you still
have the leaky old one or is that the overhauled?
Anyway 2 min sounds like a the float bowl isn't even full
when you start.
I had water in the tank once and a 540 Lyc would run at
70% rpm for nearly 6 min. I thought about fouled spark plugs as it was running
rough like that and wanted to warm up to clear them. But it didn't, so I decided
to take off, fly a turn around the boat ( to REALLY warm up the
engine), land and check mags again ( R-44 on a Tunaboat....). I take her
into a hover at around 6 min running time and right there she quit!! 10 seconds
later I would have been in the drink!
Turned out to be about 13 gallons of water in the fuel!!
My mechanic "checked" the fuel okay - my fault, I trusted him.....
However the 540 ran around 6 min with the fuel in the line
and the float bowl, until the water hit. WIWTS is 2 min is NO indication that
there is good flow into the bowl.
Your description sounds like something plugs up the fuel
line to the bowl or the float/needle is stuck halfway up or some debris in the
line (from where the fuel line connects to the carb to the
float-bowl)
IF the engine sounds good at 1500 ( no misfires, etc.),
ignition should be fine.
Do you have an air filter? Any chance something in the
airpath can flip-flop and partially plug the intake?
How long does it take until you can re-start and run it
the 2 min at 2100-rpm?
Even if your carb is new, it doesn't mean it is/was clean.
In aviation I learned to take nothing (especially if it is new) for
granted.
E.g. even with new parts it is sometimes impossible to
adjust the gap for the retarted points in a mag correctly AND time it
correctly to the engine.
The manufacturing tolerances are too big,
....sometimes.
Check your carb....
Thomas J.
----- Original Message -----
Sent: Wednesday, August 03, 2005 6:15
PM
Subject: [FlyRotary] further testing -
-lycoming O-320
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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