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Sluggish Engine Starting


Pascal

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Greetings to all.  I've asked this question in the past, but it's been a while and I can't seem to find it in the archives.  I have a 1988 M20k 252 with ~1900 total time.  Engine was overhauled at ~1100 hours.  In the past several months, I've had difficulty getting the engine to turn over when I engage the starter.  Replaced the starter motor, have a Concorde battery with about 100 hours and full charge.  What happens when I engage the starter is that it turns very slowly, labored.  As soon as it starts to get any speed at all, the engine fires up quickly.  After it spins a little, I don't have the same problem.  The engine turns over at normal pace for a hot start as well.

Any ideas?

If you think the answer is the Starter Adapter, any ideas about where to get one?  I checked replacement costs.  Most parts are unreasonably priced.  TCM new is beyond ridiculous.  If it is the Starter Adapter, does anyone know where rebuilds can be done?

Thank you very much in advance for any options or recommendations.

Pascal Budge

N33RK

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You mentioned you replaced the starter motor...what brand/model did you install?  If it's a lightweight SkyTec, it isn't surprising that you'll have issues with starter adapters.  The Energizer heavier-duty starters are the best for Continentals, generally.  Assuming, of course, this is your problem...

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I don’t know if the k model has a “shower of sparks” like my 66 e model does. That’s a good place to start looking.  I had the classical hard to start problem.  Also check wire connections at starter motor, solenoid, engine ground strap, and ignition switch. I found loose wires in my ignition switch that just needed to be tightened up. I also had a loose connection at the main starter motor cable. Has the engine “kicked back” or tried to start in reverse? 

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Never had a "kick back" that I noticed.  The starter works perfectly when the engine is warm, or if it's turned over a few times.  I don't have a problem getting the engine started once the motor can get it turning.  Usually less than 2 blades to catch.

Time for the annual, so we'll work on diagnosing the issue.

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tmo, 

I checked the capacity a couple of weeks ago on the phone with a Concorde technician, who was extremely helpful by the way.  Pretty sure the battery is not the culprit.  However, we'll do the external power option just to confirm.  Want to check and make sure the relay isn't contributing to the problem, but the hot start performance would suggest something else.

 

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1 hour ago, Pascal said:

Never had a "kick back" that I noticed.  The starter works perfectly when the engine is warm, or if it's turned over a few times.  I don't have a problem getting the engine started once the motor can get it turning.  Usually less than 2 blades to catch.

Time for the annual, so we'll work on diagnosing the issue.

As I said before...plan to get that SkyTec out of there at annual (if that's indeed what you bought - you mentioned it in your earlier post, but it wasn't clear if that's what you bought). 

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5 hours ago, StevenL757 said:

You mentioned you replaced the starter motor...what brand/model did you install?  If it's a lightweight SkyTec, it isn't surprising that you'll have issues with starter adapters.  The Energizer heavier-duty starters are the best for Continentals, generally.  Assuming, of course, this is your problem...

Interesting.  The stock Iskra motor doesn't release the shaft - you can tell because the prop is difficult to rotate backwards.  This risks damage to the starter adapter if there is a kick-back on a failed start.  The ST-4 is a high-torque version like the ST-5, and equipped with a clutch.  Prop is now easy to rotate.

The ST-3 lacked the torque to seize the shaft well for starting.

Poplar Grove recommended the ST-4 motor in place of my working Iskra, and for $700ish, why not?  Time will tell, I guess...

Precious little useful load in the Acclaim.....

-dan

Edited by exM20K
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FWIW, these are Continentals recommendations for 24V starters, this revised bulletin SIL 16-1A SIL16-1A 24V Starter Options.pdf came out after they discontinued a lighter Skytec they were favoring for awhile because of the issues with it. They now recommend the heavy Energizer but also provide option for a lighter Skytec the PM2407. Cirrus has selected the lighter Skytec because they believe it helps with the lighter composite prop. To my knowledge TCM is silent on the other Skytec offerings, the high torque ST5 and its cousin in a light weight version ST4

A bit about the Cirrus lighter weight alternative endorsed by TCM  is here: https://hartzell.aero/news-release/cirrus-aircraft-selects-sky-tecs-new-generation-pm-series-starter-standard-equipment-continental-engine-powered-cirrus-models/

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Hmmmmm...

looks like we may have covered all the bases....

Now to rake the base paths a little more.....

 

Got any details about your starter relay?

These devices have a tendency to get dirty and not deliver all the current that they are capable of...

If yours is original... with thousands of hours on it... it may be time to swap it out...(?)

Then again, all the connections from the battery to the starter are worth looking into... clean and tighten...

 

This isn’t particularly helpful advice... but may give you something to think about while you are in there....  Something isn’t delivering or receiving the power you expect it to be getting....

PP thoughts only, not a mechanic...

Best regards,

-a-

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On your first start of the day, something is preventing sufficient voltage from getting to your starter.  Really only two things can be causing that- the battery or a bad connection.

A parasitic voltage draw even with everything turned off can drain a battery so it acts like yours.  After it starts and the alternator charges the battery back to full capacity, all subsequent starts are fine.  When you did your capacity check, was it after the plane had been sitting a while, or was it shortly after flying/charging?

Dirty or loose connections can show themselves too on the first flight of a day.  Add a little heat and vibration and the connections make better contact for subsequent starts.  

Likewise, I've seen battery relays and starter relays make intermittently bad contact due to carbon buildup on the contractors.  Sometimes "exercising" the master switch and starter switch a few times will result in better current flow.  That will also let you know which one needs replacement. 

Good luck, keep us posted!

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My thanks to all for the responses and recommendations.  N201KTurbo, we will certainly include this analysis in our diagnostic this afternoon.  Done some work on proper bonding/grounding, but that's one of those things that is always a healthy review.  Austintatious, I routinely rotate the propeller before starting, specifically to make sure it isn't binding, and just to get it moving a little.

I did not install a SkyTec starter.  I purchased a refurbished Teledyne starter (646275-1) from qaa.com.  It's the heaviest of the 3 options Paul K mentioned, which is one of the reasons I wanted to try a SkyTec.  The Hartzell option looks interesting.

carusom, we'll be checking the relay in our diagnostic analysis.  Previously, I removed and cleaned the contact points really well.  Clean contacts doesn't mean it's functioning as it should, but it's one of the actions to work on.  I think it's the original.

Andy, battery was checked both shortly after use, and days/week after sitting.  What I'm not sure of yet is whether the starter remains engaged and cranking and just doesn't have the ability to translate the energy through the adapter because of the adapter, or if there is a potential voltage drain between the battery and starter.

As I said to begin with, thanks to all for the recommendations.  Very helpful.  Will share the outcome when we figure it out.

Pascal

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It is usually the battery. 

The good news is it should be easy to troubleshoot with a voltmeter. First, do you have a JPI? Did you monitor voltage when starting. If it is low, have a helper measure the voltage right at the battery during starting. And you can also measure the voltage across the starter solenoid. With enough measurements you should be able to trace it down to the actual component. Keep the mixture out so it doesn't actually start during all of these start attempts. 

How exactly was the battery checked?  There is the capacity test recommended by Concorde where the battery is drained flat and capacity calculated. And there is also a test where you can measure the voltage under a full starting current. I wouldn't really trust any other test besides these two. I have personally killed a pretty new Concorde by leaving the dome light on for a few days. It would not hold a charge after that little mistake. 

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Ok, the A&P and I did some initial diagnosing.  Battery was tested after about 5 days of non-activity.  Measured 25.2 solid, I.e., it held that voltage.  Then we disconnected the starter and checked voltage delivery to the starter by engaging the starting circuit.  Measured 24.7.  We didn’t check the voltage drop at the battery with the starter engaged.  Any inputs on how much drop there should be?  If the voltage drops more than it should, what does that mean?

I know on car batteries, there are two essential components required to be a healthy batter; voltage storage, and cranking amps.  You can have acceptable storage, but if the cranking amps are not sufficient, the battery is the problem, or vice-versa.  I assume there’s something similar with aircraft batteries, but I don’t know how to test that.

I started it again the other day.  Initially, there seems to be sufficient power delivered to the starter, at least it sounds that way.  However, it still takes a bit for the engine to actually turn over on the first attempt; very labored start.

As before, thank you all for the recommendations and ideas.  More to follow...

Pascal

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8 hours ago, Pascal said:

Ok, the A&P and I did some initial diagnosing.  Battery was tested after about 5 days of non-activity.  Measured 25.2 solid, I.e., it held that voltage.  Then we disconnected the starter and checked voltage delivery to the starter by engaging the starting circuit.  Measured 24.7.  We didn’t check the voltage drop at the battery with the starter engaged.  Any inputs on how much drop there should be?  If the voltage drops more than it should, what does that mean?

I know on car batteries, there are two essential components required to be a healthy batter; voltage storage, and cranking amps.  You can have acceptable storage, but if the cranking amps are not sufficient, the battery is the problem, or vice-versa.  I assume there’s something similar with aircraft batteries, but I don’t know how to test that.

I started it again the other day.  Initially, there seems to be sufficient power delivered to the starter, at least it sounds that way.  However, it still takes a bit for the engine to actually turn over on the first attempt; very labored start.

As before, thank you all for the recommendations and ideas.  More to follow...

Pascal

This is from Skytec starters, but should apply to all for troubleshooting.

https://skytec.aero/aircraft-starter-performance-issues/

A slipping starter adapter would have the propeller blades quivering while cranking the engine. Then it finally grabs and spins normally.

Clarence 

 

Edited by M20Doc
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I keep wondering if your mags are even trying to fire at 0deg (TDC) at the Ignition start position. if they are trying to fire at the normal 25deg BTDC that will certainly cause the starter to strain (act sluggish) during start... and ultimately fry the starter motor. Also check for loose wires at the ignition switch as well. Just my two cents, And good luck!

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  • 5 weeks later...

All,

My A&P monitored when I engaged the starter motor.  Blade was labored as I explained previously.  He came away saying he pretty confident the adapter is the problem.  We tested other potential problems with delivery of adequate power to the starter.  All indicators were “nominal” (I live in the shadow of Kennedy Space Center!).  

We also checked timing.  MAGs may have been off by a degree, or within 2 degrees of the timing recommendations in the Mooney Maintenance Manual.

So, we removed the adapter the other day and I sent it to QAA for rebuild.  I contacted several rebuild options, all of those previously mentioned in this forum.  QAA was the best option for my circumstance.  I got some very customer service oriented support from the Hartzell rep and QAA.  Housing appeared to be in good condition, along with all of the visible gears in the adapter.  I should get it back by the 18th and we’ll try to get it installed by the 23rd or so.

I’ll update after it gets installed and we get a chance to test it.

Pascal

N33RK

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Pascal,

Did you get a chance to check the starter’s relay at all?

Today, We have a similar report from @DonMuncy of slow start of his M20K... The starter was having difficulty getting current to the starter...

And it looks like the relay may be the hassle... his went from working to behaving funny in one start attempt... the relay had an obvious fault to go with it...

PP thoughts only, not a mechanic...

Best regards,

-a-

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  • 2 weeks later...

All,

Received the rebuilt Adapter yesterday and got it installed last night.  There is no further opportunity for debate.  My problem was the Adapter.  When I engaged the starter motor, the engine responded to positively I was a bit shocked.  I'm in the middle of an annual, so we did some fuel system pressure testing before I tried to start it, which meant there was more fuel in the cylinders than I would normally use.  It didn't start immediately, but it did start quickly.  There was ZERO hesitation when I engaged the starter.

I asked the technician who did the rebuild about what they found.  The spring waIMG_3318.HEICIMG_3318.HEICs "tired", and there was some minor damage to the shaft in the Adapter.  When it came back from QAA, it looked new.

The A&P is confident that was the issue.  What I can say is there is no delay or hesitation when I engage the starter now.

Robert, yes we did check the relay and found it was functioning satisfactorily.

I wish it would have been less expensive to fix, but there is it.

One other non-related item.  The exhaust shrouds were the originals, and were nearly shattered.  So, I removed them and searched for a solution.  After MUCH research, Mooney said they could manufacture replacements at about $1k per shroud!!  I removed mine and sent them to AWI in Minnesota.  They were able to refurbish them to the point that they have the appearance of "new".  They came back with 8130 documentation.  Installation was simple, and they fit perfectly in every way.  Oh, they did the refurb at a fraction of the cost to get a new pair fabricated from Mooney.

Pascal Budge

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