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Date: Wed, 03 Aug 2005 20:37:44 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: further testing - -lycoming O-320
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You might be able to eliminate the ignition systems by doing a mag check 
at high power before the problem starts, then do it again after the 
problem starts & see if you notice anything different during the 2nd check.

Do you have a primer? You can use it as an independent method of fuel 
delivery. Run the boost pump & when the rpm drops, give it a few slow 
pumps. RPM might drop slightly while the pump fills but probably won't 
if you are running the boost pump. If you really have fuel starvation, 
RPM should surge up (probably will still be rough) when you push in the 
primer knob.

How rough does it run when the problem starts? Do you have 4cyl cht 
probes? Do they stay balanced after the problem starts? If no 4probe 
cht, do you have access to a fast-responding industrial thermometer or 
laser thermometer? If it gets really rough, you might try to run it with 
the cowl off & continue to run it for 5 minutes after it gets rough. 
Then shut down & immediately measure the temps of the exhaust pipes at 
the heads. If temps don't maintain their normal spread, you might have a 
valve train path running out of slack on one cyl & holding the valve open.

Charlie

rijakits wrote:

> 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 -----
>     From: kevin lane <mailto:n3773@comcast.net>
>     To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
>     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.
>     Kevin Lane  Portland, OR
>     e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>
>
>          
>