Won’t start after running engine for a few minutes

[Nick81]

Hello MS’ers,

I have a 1981 M20K that is new to me.  I am having a problem with the plane not starting after it’s been ran for a few minutes.  The engine will turn 1/4 to 1/2 turn and stop.  If I jump the battery it starts fine and the volts are 14.1 to 14.4 while flying and I am not suspecting an alternator or battery (New).   Cables are tight and newer (2 yrs).  Any advice on what to check next? 

[Rwsavory]

When was your starter last replaced or overhauled? Not an expert, but that’s what I would look at next.

[Bolter]

Does the problem exist after a shutdown when it has run a long time?  Or only if it is run a few minutes?  There is a big difference in heat between these conditions.

[EricJ]

I'd do a capacity check on the battery.    If it has enough to start once but then won't start again until recharge it might behave like that.

 

[Fly Boomer]

2 hours ago, Nick81 said:

If I jump the battery it starts fine and the volts are 14.1 to 14.4 while flying and I am not suspecting an alternator or battery (New).

In-flight voltage just tells you that your charging system is working.  As @EricJ suggests, if you have not had a capacity check in a while, that could be a useful next step.  It takes a special tool to check the capacity.  I suspect there are a lot of batteries out there that will start an engine, but can't pass a capacity check.  There are a variety of DIY schemes for capacity checkers, but this is an example of a purpose-built machine:

https://www.aircraftspruce.com/catalog/elpages/bc6000tester.php

[Nick81]

3 hours ago, Bolter said:

Does the problem exist after a shutdown when it has run a long time?  Or only if it is run a few minutes?  There is a big difference in heat between these conditions.

I flew for 1:40 min and was unable to restart.  I’ll check it from a. Cold start today. Thank you for you response. 

[Nick81]

2 hours ago, Fly Boomer said:

In-flight voltage just tells you that your charging system is working.  As @EricJ suggests, if you have not had a capacity check in a while, that could be a useful next step.  It takes a special tool to check the capacity.  I suspect there are a lot of batteries out there that will start an engine, but can't pass a capacity check.  There are a variety of DIY schemes for capacity checkers, but this is an example of a purpose-built machine:

https://www.aircraftspruce.com/catalog/elpages/bc6000tester.php

Battery is new, less than 1 month old. No cap check. 

[Nick81]

3 hours ago, Bolter said:

Does the problem exist after a shutdown when it has run a long time?  Or only if it is run a few minutes?  There is a big difference in heat between these conditions.

I am going to run it up later today and check this.    Thank you for your response. 

[Hank]

Welcome to the club! Many people have trouble with hot starts. Consider googling for Lycoming hot start mooneyspace, there are even some videos linked here.

Good luck!

[Fly Boomer]

3 hours ago, Nick81 said:

Battery is new, less than 1 month old. No cap check. 

I'm usually suspicious of new components, but there isn't much that can go wrong with a new battery.

[Meshach]

4 hours ago, Hank said:

Welcome to the club! Many people have trouble with hot starts. Consider googling for Lycoming hot start mooneyspace, there are even some videos linked here.

Good luck!

OP says the engine will only turn over 1/4 to 1/2 round…. Doesn’t sound like a hot start issue 

[MarkD34M]

When I owned my 231, I had this problem intermittently. It was traced to the starter adaptor which was slipping. Listen for the noise and if so, do not continue to keep cranking as my understanding (or recollection) is that over time. they can create metal shavings which could find their way into the engine. They can be rebuilt. 

[Z W]

The proper way to diagnose this is to start at the battery and verify proper voltage all the way to the starter to find your faulty component.  Requires a mulitimeter and some patience, and maybe a helper to verify voltage while trying to crank the starter. Check all connections along the way for security and corrosion.  A loose connection could cause what you're seeing.  I would also check the main grounding cable in the tail, bad grounds cause lots of problems.

Having been through this recently, I would suspect your starter solenoid.  It is mounted on the firewall in front of the co-pilot's footwell, most likely inside the cabin, or possibly in the engine compartment on some models.  It may be intermittently working, or providing enough connection to only work sometimes.

If you have 12v to the solenoid, but not after, it's your problem.  If you have 12v to the starter while the key is in the crank position, it's your problem.

Drawings and part numbers for the solenoid are below.  I found that neither 24059 nor 6041H-105A are readily available and ended up getting a Lamar FAA/PMA replacement from Aircraft Spruce:

https://www.aircraftspruce.com/catalog/eppages/sts-12s24s.php?clickkey=8060

I found a lot of bad and corroded old wiring, old crusty solenoids, and a couple NAPA auto parts solenoids installed by A&P's that match the 24059 part number but are now sold as tractor parts.  Replaced it all with FAA/PMA items and now it cranks better than it ever has.

Good luck!

 

 

 

[A64Pilot]

13 hours ago, MarkD34M said:

When I owned my 231, I had this problem intermittently. It was traced to the starter adaptor which was slipping. Listen for the noise and if so, do not continue to keep cranking as my understanding (or recollection) is that over time. they can create metal shavings which could find their way into the engine. They can be rebuilt. 

Heed this warning because if that’s it it can lead to an overhaul or in flight failure.

[Shadrach]

19 hours ago, Hank said:

Welcome to the club! Many people have trouble with hot starts. Consider googling for Lycoming hot start mooneyspace, there are even some videos linked here.

Good luck!

 Hank, he’s flying a Continental turbo…

[Nick81]

On 1/19/2024 at 4:00 AM, Z W said:

The proper way to diagnose this is to start at the battery and verify proper voltage all the way to the starter to find your faulty component.  Requires a mulitimeter and some patience, and maybe a helper to verify voltage while trying to crank the starter. Check all connections along the way for security and corrosion.  A loose connection could cause what you're seeing.  I would also check the main grounding cable in the tail, bad grounds cause lots of problems.

Having been through this recently, I would suspect your starter solenoid.  It is mounted on the firewall in front of the co-pilot's footwell, most likely inside the cabin, or possibly in the engine compartment on some models.  It may be intermittently working, or providing enough connection to only work sometimes.

If you have 12v to the solenoid, but not after, it's your problem.  If you have 12v to the starter while the key is in the crank position, it's your problem.

Drawings and part numbers for the solenoid are below.  I found that neither 24059 nor 6041H-105A are readily available and ended up getting a Lamar FAA/PMA replacement from Aircraft Spruce:

https://www.aircraftspruce.com/catalog/eppages/sts-12s24s.php?clickkey=8060

I found a lot of bad and corroded old wiring, old crusty solenoids, and a couple NAPA auto parts solenoids installed by A&P's that match the 24059 part number but are now sold as tractor parts.  Replaced it all with FAA/PMA items and now it cranks better than it ever has.

Good luck!

 

 

 

Great response and thank you for the diagram!

[Nick81]

On 1/18/2024 at 8:02 AM, Nick81 said:

Hello MS’ers,

I have a 1981 M20K that is new to me.  I am having a problem with the plane not starting after it’s been ran for a few minutes.  The engine will turn 1/4 to 1/2 turn and stop.  If I jump the battery it starts fine and the volts are 14.1 to 14.4 while flying and I am not suspecting an alternator or battery (New).   Cables are tight and newer (2 yrs).  Any advice on what to check next? 

It turns out this problem was caused by loose ground wires and loose wires near the battery.  They weren’t able to move freely but when tugged on they were able to be moved.   

[Mcstealth]

48 minutes ago, Nick81 said:

It turns out this problem was caused by loose ground wires and loose wires near the battery.  They weren’t able to move freely but when tugged on they were able to be moved.   

Congratulations. 

[PT20J]

One thing I have learned is that many electrical problems are caused by wiring issues. And, they are inexpensive to fix! 

[Fly Boomer]

8 hours ago, Nick81 said:

It turns out this problem was caused by loose ground wires and loose wires near the battery.  They weren’t able to move freely but when tugged on they were able to be moved.   

Thanks for closing the loop!

[PeteMc]

6 hours ago, PT20J said:

One thing I have learned is that many electrical problems are caused by wiring issues. And, they are inexpensive to fix! 

Wellll....  Okay, AFTER you find them, yes, they are usually inexpensive to fix!