Mooney starting problem

[garysuperpilot]

Been having problem starting my 67 m20f mooney. Used to start with 5 second prime and start right up. Lately been taking much more prime until this week could not start the plane without flood type start. Finally started the plane flew four hours without incident, then on landing the engine quit when I pulled back the throttle to land. Towed the plane back to the hanger and could not start the plane,hot or cold. Mechanic is checking shower of sparks but seems like more of a fuel issue. Any thoughts would be appreciated. Forty hours smoh but I don't think the fuel system was overhauled at that time so that may be an issue as well. Thanks

[mike_elliott]

It does sound fuel related based on your landing shutdown. Do you have an engine monitor? If so, can you download the data and see what the EGT's were at idle? It sounds suspiciously like a stuck needle valve in the servo on what little data we have, causing a lean condition.

As you know, it only take three things to make the motor fire - air, fuel and spark. One of them is messed up, but fortunately, any competent mechanic should get to the root of it very quickly.

[garysuperpilot]

The servo was the first suspect. The mechanic said that was only serviceable by an overhaul shop at 1200-1500 just for the shop. I think he wanted to be sure before condemning the servo as he didn't know of any way to really check the unit. He will look at it this Monday and hopefully determine the problem. Unfortunately I don't have an engine monitor to help. Let you know what we find. Thanks

[Wildhorsesracing]

I had a similar problem and it was the wire from the switch to the retard breaker points in the Magneto - replaced the wire and it was fine.  

[orionflt]

Servo can be checked using a graduated cylinder, the procedures can be found online. Also check the flow divider to make sure that is not clogged. It does sound like a servo based on what you descried.

[tomn]

Servo can be checked using a graduated cylinder, the procedures can be found online. Also check the flow divider to make sure that is not clogged. It does sound like a servo based on what you descried.

+1 Sounds like the servo to me.

[Alan Fox]

Check the flow and pressures , unfortunately people just guess in this business....

[N201MKTurbo]

First, never prime the engine. You will flood it every time.

If you haven't flown it for a few days, you can get fuel pressure by setting the throttle and mixture to cutoff and running the electric pump until you show pressure.

Have you adjusted the idle mixture and speed? They have a big effect on how the servo performs. It usually takes about an half hour and you have to start and run the engine five to ten times.

The true test is how slow the engine will idle. Anything under 500 RPM is good. I just did mine a few week ago and it would idle at 300. I ser it back to 400 so it doesn't die on rollout.

If your engine dies on landing immediately shut off the electric pump so you don't flood the engine.

[orionflt]

First, never prime the engine. You will flood it every time.

If you haven't flown it for a few days, you can get fuel pressure by setting the throttle and mixture to cutoff and running the electric pump until you show pressure.

Have you adjusted the idle mixture and speed? They have a big effect on how the servo performs. It usually takes about an half hour and you have to start and run the engine five to ten times.

The true test is how slow the engine will idle. Anything under 500 RPM is good. I just did mine a few week ago and it would idle at 300. I ser it back to 400 so it doesn't die on rollout.

If your engine dies on landing immediately shut off the electric pump so you don't flood the engine.

You minimum idle should be set for between 700-750 with the mixture adjusted so that you get a 25-50 rpm rise when you pull the mixture to idle cut off, if you have everything adjusted so you can get tha engine to idle below 500 rpm then your top end is out of adjustment and is probably way too rich.

Brian

[N201MKTurbo]

If your idle is adjusted that high your airplane will use twice as much runway to land.

The mixture at higher power is adjusted with the red knob next to your right knee.

[orionflt]

If your idle is adjusted that high your airplane will use twice as much runway to land.

The mixture at higher power is adjusted with the red knob next to your right knee.

700-750 is the engine manufactures and mooney service manual settings, I think the guys that designed the engine and al mooneys engineers knew what they were doing when they decided that they were the optimum numbers to use. Also if your that rich that you need to lean it at high power settings your just setting your self up for an engine out situation on a go around. Not the best time to loose an engine because it is running too rich and your too busy with the go around to lean it out.

[N201MKTurbo]

 Also if your that rich that you need to lean it at high power settings your just setting your self up for an engine out situation on a go around. Not the best time to loose an engine because it is running too rich and your too busy with the go around to lean it out.

 

What are you talking about?

 

I was talking about adjusting the idle mixture on an RSA5 servo. The worst thing you can do if you screw it up is make the engine so it won't idle. It has virtually no effect on the mixture at throttle settings above idle. I have been trained on this servo BTW it is part of the curriculum for the A&P license.

 

If you want to know more AC65-12A has a whole chapter on it.

[garysuperpilot]

Ok gentleman, we have the plane squared away and what we found was unexpected. I worked with the mechanic Monday and we could not get spark out of left mag , which is the one set for the vibrator. Checked all the normal things associated with the electrical system and ultimately found the leads on the left mag were reversed. Apparently, when the plane had the engine overhaul it was wired wrong at that time. We were impressed that the engine started the way it was at all. We readjusted mag timing and found the mixture setting at idle too lean. Guess that contributed to the plane stalling at idle last time I landed. I will be flying very close and above the field till I feel comfortable with the plane again. I really enjoy my mooney and look forward to flying her for years to come. Thank you all for your help. Mooney owners are the best.

[Shadrach]

First, never prime the engine. You will flood it every time.

If you haven't flown it for a few days, you can get fuel pressure by setting the throttle and mixture to cutoff and running the electric pump until you show pressure.

Have you adjusted the idle mixture and speed? They have a big effect on how the servo performs. It usually takes about an half hour and you have to start and run the engine five to ten times.

The true test is how slow the engine will idle. Anything under 500 RPM is good. I just did mine a few week ago and it would idle at 300. I ser it back to 400 so it doesn't die on rollout.

If your engine dies on landing immediately shut off the electric pump so you don't flood the engine.

I've been flying a Lyc IO360 for a long time and the notion that they never need a prime is uniquely yours...  running the fuel pump with the mixture at idle cut-off and the throttle closed does little to nothing to deliver fuel to the distributor or the cylinders.  Are you familiar with how the bendix RSA injection system operates?  The only time I do not prime is for a hot start. 

[N201MKTurbo]

I've been flying an Lyc IO360 for a long time and the notion that they never need a prime is uniquely yours...  running the fuel pump witht he mixture at idle cut-off and the throttle closed does little to nothing to deliver fuel to the distributor or the cylinders.  Are you familiar with how the bendix RSA injection system operates?  The only time I do not prime is for a hot start. 

 

Well the Lycoming IO-360 with the RSA-5 injector is a very tough and reliable system and will work nomatter what you do with it.

[orionflt]

Ok gentleman, we have the plane squared away and what we found was unexpected. I worked with the mechanic Monday and we could not get spark out of left mag , which is the one set for the vibrator. Checked all the normal things associated with the electrical system and ultimately found the leads on the left mag were reversed. Apparently, when the plane had the engine overhaul it was wired wrong at that time. We were impressed that the engine started the way it was at all. We readjusted mag timing and found the mixture setting at idle too lean. Guess that contributed to the plane stalling at idle last time I landed. I will be flying very close and above the field till I feel comfortable with the plane again. I really enjoy my mooney and look forward to flying her for years to come. Thank you all for your help. Mooney owners are the best.

Glad you got it figured out, sounds like it was previously starting when you released the key, glad you never experienced any kick back and that you now have it fixed.

[Shadrach]

700-750 is the engine manufactures and mooney service manual settings, I think the guys that designed the engine and al mooneys engineers knew what they were doing when they decided that they were the optimum numbers to use. Also if your that rich that you need to lean it at high power settings your just setting your self up for an engine out situation on a go around. Not the best time to loose an engine because it is running too rich and your too busy with the go around to lean it out.

If you're "that rich that you need to lean it at high power settings" Then you have a problem with the servo. There is no adjustment for high power Max FF...it's either in spec or there is a mechanical problem (center body seal leakage) within the servo...

[Shadrach]

First, never prime the engine. You will flood it every time.

If you haven't flown it for a few days, you can get fuel pressure by setting the throttle and mixture to cutoff and running the electric pump until you show pressure.

 

 

What exactly does having pressure from the pump to the idle cut-off valve do for you?  If you run the boost pump at idle cut off, the servo sees no fuel beyond the idle cutt off valve. If you run the Boost pump at full rich with the throttle closed, the servo gets unmetered fuel through a small oriface, but would likely take consideable time to build enough pressure to unseat the valve at the flow divider and allow fuel to the cylinders.  So I'm curious as to the theory behind your advice.  Is it just to verify the fuel pump is pumping fuel.  Also given that you don't ever prime, when during the process do you allow fuel into the engine?  Do you just crank it and go rich at some point? Do you set the mixture full rich and crank?  The engine will certaily start if you just crank it at full rich under cool, high pressure conditions but when it's hot and muggy, not so much.

[orionflt]

If you're "that rich that you need to lean it at high power settings" Then you have a problem with the servo. There is no adjustment for high power Max FF...it's either in spec or there is a mechanical problem (center body seal leakage) within the servo...

You are correct, what I posted really did not express what I was trying to say. In a nut shell my point was messing with the recommended settings is not a good idea, yes you can get the plane to idle a lot lower but it will affect the overall operation. as for my poorly worded blurb on engine loss during a go around, if your down at 3-400 rpm on approach and suddenly give the aircraft full throttle to go around the engine may studder or stall due the required adjustments to the mixture to keep it running at such a low RPM and the sudden introduction when the go around is initiated. Hope I said it better this time.

[Shadrach]

You are correct, what I posted really did not express what I was trying to say. In a nut shell my point was messing with the recommended settings is not a good idea, yes you can get the plane to idle a lot lower but it will affect the overall operation. as for my poorly worded blurb on engine loss during a go around, if your down at 3-400 rpm on approach and suddenly give the aircraft full throttle to go around the engine may studder or stall due the required adjustments to the mixture to keep it running at such a low RPM and the sudden introduction when the go around is initiated. Hope I said it better this time.

Orion,

I get what you're saying. If the the throttle's is closed and the servo is puking fuel through the motor, it could theroretically have all kinds of negative impacts of the throttle response, including loading up the plugs. However, I would say, that I cannot envision a scenario where a Mooney would ever see 3-400 RPM in flight (maybe if executing a power off tail slide :-)). I'd also submit that there is no good reason to ever run a lycoming below 900 RPM. That does to mean that we want to set it for 900 RPM though. My tack shows just over 600rpm at idle when the plane is not moving. I have not opened my MM to check the what's reccomended, but I'm betting that within the +/- specs. My idle mixture is set up in such a way that I get ~50rpm rise when going to idle cutoff which is desirable for throttle response if you need to firewal it from closed throttle. However, for taxi and normal ground ops, it's quite a bit richer than needed. I taxi with the mixture knob nearly half way out under most contitions.

[N201MKTurbo]

You can significantly shorten your landing distance by setting the idle slower.

 

Part of the procedure I use to set the idle mixture is to be sure it does not stumble coming off of idle. 

 

I know there a lot of people who land with power, I don't.  Every landing I have the power at idle from about 1/4 mile out.

 

I can always make the second turnoff without brakes.

[garysuperpilot]

Flew the mooney again today, flies fine, 700rpm idle which seems to be what's recommended. Haven't had the mooney long but have owned a Cessna and a Cherokee for the last 14 years. I have personally never felt comfortable "dragging in" a plane on final at idle speed. If there was a marginal length where it was necessary to get down in a short runway, maybe.... I guess if I'm landing on a 4000-5000 ' runway which is typical for where I fly, I'd like to know I can make the runway rather than be in a hurry to make an early turnoff. Just my opinion. Hate to lose that engine at my 400 rpm idle on 1/4 mile final. I guess we all fly where we feel most comfortable .