Engine Dies after Run-up

NKTFlyer

NKTFlyer

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NKTFlyer
Gentlemen and Ladies of the Blue Site,

1965 Mooney M20E with original Lycoming IO-360-A1A. We all bring the throttle all the way to the idle stop at the end of the run-up to ensure it doesn't do something whacky (like die), but I always thought of the possibility more prevalent in a carbureted engine with the carb heat on. This one is fuel injected. It happened on a Saturday afternoon, and the local shop doesn't open until Monday. I'm obviously not flying it somewhere else. Any experienced members want to take a SWAG at what might be the root cause?
 
I'm no expert, but there doesn't seem to be enough useful information to even guess as to the cause.
 
Idle fuel air ratio/idle needs adjustment....no biggie. I bet it runs fine just above the idle stop.
 
Yea not enough information to accurately assess it. Get the idle setting looked at, as it might be set too low causing it to stumble before quitting altogether.

Did it hold a specific RPM setting before dying or did it just quit immediately upon closing the throttle?
 
Don't know and can't guess root cause. Have seen various problems with fuel injection systems. If you really want guesses from the peanut gallery make a declarative statement about the cause and then watch all the naysayers and egotists proclaim you are wrong along with explaining in detail how they are right.

Other thing to say is good job with the decision not to fly when something didn't perform as expected during the pre-flight checks. It can be a difficult decision for some folks to cancel a flight at that point.
 
Ryanb said:
Yea not enough information to accurately assess it. Get the idle setting looked at, as it might be set too low causing it to stumble before quitting altogether.

Did it hold a specific RPM setting before dying or did it just quit immediately upon closing the throttle?
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The place I worked years ago bought an airplane, boss flew it home, and he said the idle needed to be adjusted because it kept quitting when he brought it back to idle...started up fine, but quit after the runup and on the landing rollout.

After I had it quit on a go around at Vx and 75 feet :eek: we discovered it wasn't the idle setting. It was a plugged fuel tank vent.
 
Two planes from the same rental place here in FL had that problem. Guess where I don't rent from anymore?

:)
 
Sometimes the idle speed just isn't set high enough and the engine will die. In that case I wouldn't pull the throttle all the way back until I was prepared for the engine to stop. No different than mixture.
 
Stewartb said:
Sometimes the idle speed just isn't set high enough and the engine will die. In that case I wouldn't pull the throttle all the way back until I was prepared for the engine to stop. No different than mixture.
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Isn't that dangerous? Idle should = idle, not off, no?
 
Caramon13 said:
Isn't that dangerous? Idle should = idle, not off, no?
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I believe the reason its such a big deal is that once you close the throttle on final, if the engine quits, you've got no option to go around.

I got some dual instruction from a guy with a Super Decathlon once who's take on it was that as long as the prop would windmill, you just had to get the RPM off idle quickly after it quit flying. It worked for him. But, I'd just get the throttle properly rigged.
 
Stewartb said:
Sometimes the idle speed just isn't set high enough and the engine will die. In that case I wouldn't pull the throttle all the way back until I was prepared for the engine to stop. No different than mixture.
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In that case you need to get it corrected because that shouldn't be normal operation. The engine should quit when the mix is pulled to cutoff, not the throttle.
wilkersk said:
I believe the reason its such a big deal is that once you close the throttle on final, if the engine quits, you've got no option to go around.

I got some dual instruction from a guy with a Super Decathlon once who's take on it was that as long as the prop would windmill, you just had to get the RPM off idle quickly after it quit flying. It worked for him. But, I'd just get the throttle properly rigged.
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That's exactly why Caramon questioned it, but that doesn't answer his question.
 
Eh, engines are only mandatory for takeoff and cruise where you won't have the throttle back anyway. :rolleyes:
 
You usually don't have the aircraft stationary at idle unless you are on the ground, so it isn't too much of a problem. When the prop turning, the engine won't die with the throttle at idle. When I had a balky idle-mixture setting we'd only notice it after rolling out on landing and the engine would stop once we'd slowed to a near stop.

Anyhow, it needs to be looked at. If it happens when the engine is cold, you're probably either way to lean, or the throttle stop is way too low. What RPM are you at prior to it dying. Most engines want like 700 RPM or so. If it dies only after the engine is hot, it's quite possilbe the idle mixture is too rich.

Note the mixture control doesn't do much at idle, there's usually a separate idle loop. Until you move the mixture to the "idle cut off" you're not restricting the fuel flow at that setting.
 
I had a plane that I could make quit at run-up if I pulled the throttle back abruptly. I never thought much of it because I never pull the throttle all the way out abruptly when flying. Pilot controls sometimes require pilots to think about how to use those controls. I'd want to get the idle adjusted up but I wouldn't ground it in the interim. That's just my opinion from my perspective. Everyone else should do what they feel is best.
 
flyingron said:
You usually don't have the aircraft stationary at idle unless you are on the ground, so it isn't too much of a problem. When the prop turning, the engine won't die with the throttle at idle. When I had a balky idle-mixture setting we'd only notice it after rolling out on landing and the engine would stop once we'd slowed to a near stop.

Anyhow, it needs to be looked at. If it happens when the engine is cold, you're probably either way to lean, or the throttle stop is way too low. What RPM are you at prior to it dying. Most engines want like 700 RPM or so. If it dies only after the engine is hot, it's quite possilbe the idle mixture is too rich.

Note the mixture control doesn't do much at idle, there's usually a separate idle loop. Until you move the mixture to the "idle cut off" you're not restricting the fuel flow at that setting.
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It probably does die without throttle, but starts back up instantly with throttle - no real difference. Unless there is something else wrong. I'd want to have it working correctly before I flew it - Just to rule out other potentially problems.
 
Different strokes for different folks. When I bought my mooney I found out it wouldn't idle all the way back with carb heat in. Last owner said "don't do that". It took me about 20 minutes to adjust it so it kept running. I want my engine to run no matter what. But that's just me.
 
Salty said:
Different strokes for different folks. When I bought my mooney I found out it wouldn't idle all the way back with carb heat in. Last owner said "don't do that". I fixed it in about 20 minutes. I want my engine to run no matter what. But that's just me.
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I guess that's sorta what I was getting at with my question. I guess there are situations where it WON'T matter since the prop is still turning, etc. But I know the planes I fly have an idle / check step in the checklist and if it doesn't idle, it doesn't "check".
 
Piston return spring is bad. At idle you're not generating enough pressure to sustain engine operation. Since the spring is bad, it can't compensate for the lack of internal pressure in the cylinder.

You can confirm by getting a sample of the exhaust gas and taking it to your AP. Should read a little higher than normal due to the residue sitting in the chamber longer.
 
Does Lycoming have an equivalent to TCM's SID97-3F Fuel Flow Adj specs and instructions?
Until I did that with my IO-520, mine would die on the runway during rollout.
 
ircphoenix said:
Piston return spring is bad. At idle you're not generating enough pressure to sustain engine operation. Since the spring is bad, it can't compensate for the lack of internal pressure in the cylinder.

You can confirm by getting a sample of the exhaust gas and taking it to your AP. Should read a little higher than normal due to the residue sitting in the chamber longer.
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Could be the muffler bearings too
 
Ryanb said:
In that case you need to get it corrected because that shouldn't be normal operation. The engine should quit when the mix is pulled to cutoff, not the throttle.

That's exactly why Caramon questioned it, but that doesn't answer his question.
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His question was "isn't that dangerous?" I figured the answer was self evident. But, do you really want a direct answer, or numbers for your post count?
 
You have to ask what's the point of checking something if you are going to takeoff anyway. That's the definition of complacency.
 
It's the bypass valve. You'll need so gauze pads, some ball bearings and some thirty weight oil, Pennzoil....no, make that Quaker State.
 
ircphoenix said:
Piston return spring is bad. At idle you're not generating enough pressure to sustain engine operation. Since the spring is bad, it can't compensate for the lack of internal pressure in the cylinder.

You can confirm by getting a sample of the exhaust gas and taking it to your AP. Should read a little higher than normal due to the residue sitting in the chamber longer.
Click to expand...

Might be the wrong powerband, too...
 
I see the update that this was ultimately limited to an idle issue. I did want to point out that some of the suggestions ran on the apparent assumption that this was an idle issue only and would stay an idle issue. My concern would be "what if something else is causing this, that is going to progress to an issue affecting more than just idle?" While very few (none?) planes are squawk-free, anything that affects engine operation, to me, is a no-go.
 
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