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went out to start my plane the other day and it wouldnt turn over. The SOS buzzed but no movement of the prop and nothing engaged the ring gear. i assumed it was a battery but when i load tested the battery it was good so i checked out to the power relay and all checked good. i need to know where the starter relay is for the next thing to check and any other suggestions will be greatly appreciated. it is a 1695 m20E

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SkyTec troubleshooting guide is best place to start and, if necessary, the ST folks are great to work with.

Our ($/painful) road to fixing a similar start issue, also E model, led to rebuilding the push-to-start ignition switch.  With the key pushed/turned, back off the pressure a little and see if it engages.

Mike V

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1 hour ago, JMV said:

SkyTec troubleshooting guide is best place to start and, if necessary, the ST folks are great to work with.

Our ($/painful) road to fixing a similar start issue, also E model, led to rebuilding the push-to-start ignition switch.  With the key pushed/turned, back off the pressure a little and see if it engages.

Mike V

The push to start function in these Bendix switches was not a brilliant design to put in an aircraft- in order for the switch to function properly with low effort, the copper starter contacts in the switch have to be dry, clean of corrosion. (the pressing action of the switch does nothing to wipe or clean the starter contacts).

After taking one apart, I can’t believe more pilots aren’t complaining about them being somewhat intermittent.

If you do open up the switch, do not lubricate the area where the starter contacts are- it will inhibit its function.

+1 for checking the switch

51B4DF83-E10A-4952-AC7D-A2207662664C.jpeg

Edited by PilotCoyote
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Welcome aboard, Mike.

+1 on cleaning the Start switch...

Really old design, wears incredibly well, often confuses the guy rewiring it...

The first failure the new owner got with my old M20C... the push to start function had given up... the day he went to fly it away...

PP thoughts only...

Best regards,

-a-

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4 hours ago, Planegary said:

Thanks for that info I will definitely check out the press start function when I get off tour

If your starter solenoid is activating then the switch is not a the problem.  

The trouble shooting guide is your friend.

Do not tear into the ignition switch without guidance from a pro. There are small parts that can be lost and the switch is not inexpensive to replace. I disagree with @PilotCoyote on the switch design. Yes they fail occasionally, but considering most have been in service in excess 50 years or more they’re pretty reliable. Lots of planes flying around on their 4th overhaul with the original ignition switch.  I recently cleaned mine. First time I’ve done it in 15 years, it’s definite the original switch.

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Finally got home and began checking the starter problem

1 battery checked good

2 put load test on output side of power relay to check battery output thru relay and checked good

3 disconnected input side of starter relay and saw a significant load drop on cable before relay

with this info it seems like the problem is the cable between relays bu I find it difficult to think cable has failed. Would this be possible or could it be the lugs clamped onto the cable being the problem? ( yes I did clean the lugs) :-)

any thoughts or suggestions would be appreciated

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Lugs can go bad. corrosion can reduce the ability to carry amps.    Also the master solenoid can make contact, but not good contact.  same with starter solenoid.   corrosion/arcing is how they get to be bad.   The master is expensive, but I think I found it at McMaster one time for less money.   Some people can put long screws through battery cables and hoses.

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If you have it down to the cable, from beginning to end, including lugs...

Can you put a jumper cable there to see if the jumper cable handles the load better...?

This would prove the existing cable isn’t up to the job...

Pulling the cable out makes sense when you know it is the problem...

Fixing or replacing it makes the next challenge.

PP thoughts only, not a mechanic...

Best regards,

-a-

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I agree with Yetti about the lugs.  Solenoids can intermittently make good contact.   Are you confident you had a good ground during the voltage drop test?    Also Aircraft Spruce sells Sky-Tec/Lamar FAA-PMA approved main (continuous duty) and starter relays for around $75. 

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7 hours ago, DMM said:

I agree with Yetti about the lugs.  Solenoids can intermittently make good contact.   Are you confident you had a good ground during the voltage drop test?    Also Aircraft Spruce sells Sky-Tec/Lamar FAA-PMA approved main (continuous duty) and starter relays for around $75. 

I had experience with a fleet of about 200 trucks using continuous duty solenoids.  We found the metal can ones pretty much sucked.  The Sky-tec ones are metal can.

 

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The first step with a starter for me is run a jumper cable from the battery to the starter and see if it turns.  Ensure you don’t kill yourself doing this.  Takes out all the middle men.  

If it doesn’t whack the starter a couple of times with a rubber mallet.  Try again.  If it doesn’t start new starter.  If it does after whacking new starter.  

If it works right away then you know the problem is upstream and can trouble shoot from there.  It clears out the starter as the problem and takes less then five minutes. 

Edited by M20F
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Well I finally found the problem. The lug attaching the power to the input side of the starter relay was not making a good connection. A buddy had a crimped and we recrimped the lug and all is well. Am glad to have found the problem. The mechanic found there was some resistance in both the power relay and the starter relay so I replaced both of those as well. Should be good to go now

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  • 4 weeks later...

Update to my problem. I only thought I had found the issue. I went to take the plane out for gas and all was fine til I tried to start it to fly home.the shop spent all day chasing the gremlin. It seems that the main cable from the power relay to the starter relay has a problem intermittently and checks good until put under load. The shop is gonna let me change out the cable since it is already in their shop and opened up to help offset some costs. Can’t wait to see what is causing the problem but when you test it one time it seems ok and next time not but the cable is the only thing left not replaced and it is original so it is coming out. Pics will be coming of what I find

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Is there a circuit breaker anywhere in this mix?  They wear out and only show the problem under load by dropping voltage and eventually popping.  

I don’t have the diagram in front of me, but are You sure the starter solenoid is getting good power from the switch through your starter circuit breaker?

Circuit breaker would account for this being only under load and sometimes working.

Edited by Ragsf15e
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Thermal circuit breakers supply some resistance to generate heat...

more current, more heat... until the temp rises enough to pop the CB mechanism...

It is quite possible that a faulty CB, or bad connection is inhibiting electron flow...

expect a CB to be associated with the starter... 

Similar electrical layout to the M20E, But actually from a C.... I don’t see the amp rating that may go with that...

know that hot days, make the CBs even more sensitive...

Rags may be onto something worth confirming... 

PP thoughts only, not a mechanic...

Best regards,

-a-

 

586D6A42-84B8-4E1F-9E44-A15E9A196ED6.png

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the original lycoming starter and it appears that is the culprit. yday after pulling most of the interior out the shop owner came by and told me to stop that he wasnt convinced the cable was the problem and long story short we are gonna put a replacement starter on the plane on mon. he found the starter had the small armature shaft and we could see the bushing holding it was shot so he thinks the armature is dropping onto the field and that is my problem. we will know on mon

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the problem has finally been located. It was the airframe to engine ground. I hope this might help somebody else not have to go thru all the hair pulling (dont have any to spare) that I went thru. Truly a learning experience for me since I had thoroughly cleaned and tested the battery to frame ground

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