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M20C not cranking


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Apologies in advance because I know this is probably a dead horse but, have a new-to-me 67 C that will not crank when the ignition switch is pushed in and all the way to the right. Almost got stranded on a cross country, had a mechanic come out after hours and he got it to crank on the first try. Got the plane home and it’s back to no cranking (cold start). I can hear the buzz and the click of what I imagine is the starter solenoid? Battery is a brand new Concorde and I have checked cleaned the wires/leads from the battery to the starter solenoid/starter. Please correct me if I’m wrong but the buzz/click would indicate the ignition switch is working, but something is busted downstream of that. Any ideas on what to check next would be greatly appreciated. Thank you.

 

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Welcome aboard DR...

why is it a dead horse?

If it is, you still want a live horse, right?

 

There are about a dozen things that can cause this...

All 13 of them have been covered in several threads...

Some are simple, some are complex...

How handy are you with a volt meter?

Ever clean electronic connections before?

How driven are you to fix some things yourself?

Do you have a mechanic that you can work with?

Typical things to brush up on...

  • Ignition switch (more complex than you described, it may be partially working... you need it to all be working)
  • starter relay (some click, but don’t deliver enough amps)
  • battery (some show proper volts, but lack capacity)
  • Shower of sparks (won’t interfere with the starter actually working)
  • starter
  • cables
  • grounds
  • Logs... (start checking on what you have, How aged they may be, and what updates may make sense)
  • What starter do you have? ( How many years and hours and whatever you can find out)

Start at one end and see how far the electricity gets...

If it gets all the way to the starter, it could be dirty connections...

Keep in mind the prop is lethal... do not trust it to be safe. Even when the keys are in your hand...

PP thoughts only, not a mechanic. Skip forward one post to get some excellent insight from an actual M20Doc... :)

Best regards,

-a-

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M20Doc is spot on.  If you have an OEM starter (Bendix?), get rid of it and get a Skytec.  Years ago when I bought my M20C I had the same problem:  The starter was sluggish and slow-cranking, and drained even a new battery fast.  I've had my Skytec starter for over 20 years now and it cranks at about twice the speed of the original.  Zero maintenance, zero problems.

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Some clarity in your problem is needed:  does it not crank (engine doesn't turn over, prop still) or does it turn over but not start? These are different issues withndifferent solutions. The first is either electricity or ground to the starter or the ignition switch (electricity, ground, internal function); the latter could be thenignition switch as above, magneto condition, Shower of Sparks, plugs, fuel (mechanical fuel pump, carburetor issues, etc.) . . .

 

Edited by Hank
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The buzz is likely the Shower of Sparks which operates only when the key is in start position.  It is good you hear that it works. 

As others have suggested — Next  you trace the voltage from the battery to the starter relay to the starter. 

 

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couple of things to check because it sounds like the starter is not dead, or totally dead. after you try to start the plane, is the starter gear engaged on the fly wheel? the older starters will stay engaged until centrifugal force from the running engine kicks it back. if it is and you have a dead spot on the starter, rotating the prop can move the starter off the dead spot and allow it to start. 

another possibility is the push to start contacts in the switch, if these contacts are not being made the start solenoid will not engage, providing power to the starter.

the last possibility I have for you is a bad ground to the engine that is not allowing the started to get enough of a circuit to rotate the starter. the ground should go from the battery to the engine and then from the engine to the airframe. 

Brian

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Went out to troubleshoot and turned the key just for fun. Plane cranked and prop spun the first time no problem. Still went through the steps from sky tec and the numbers I got were:

12.96V on the battery

10.39V on the starter

11.43V from battery to master

.02V across the master (I may have goofed that up?)

11.3 V Master to bus

10.96V from contactor to starter 

 Electrical is not my strong point, but if anyone sees something glaring please let me know and thanks again for all the help. My A&P gets back Friday so hopefully that’ll help.

 

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Glaring...

The full charge voltage of the battery isn’t getting to the starter...

But these can be misleading...

The voltage numbers here are static when being measured...

The starter needs strong voltage when it is being used... a tad more challenging when electrical isn’t your strong point...

have your mechanic measure the voltages at the same points while somebody turns the key...

If there is a dirty connection, the voltage may drop significantly, showing what needs to be cleaned or updated...

The system needs a fire hose for the electrons to pass... something in there is causing a garden hose like restriction... how are your plumbing skills? :)

Be extra careful... miscommunication or hitting the starter accidentally can be disastrous... do not rush, do not assume... verify all communications...

PP thoughts only, not a mechanic... 

best rgerads,

-a-

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Thank you for the information. Those are all numbers measured while the starter was cranking. That’s why the drop across the master stuck out as either erroneous or the culprit. I’ll be going through and cleaning everything tomorrow to see if that makes a difference. 

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DR,

where I may be getting lost with your data...

you are not very clear with what you have done exactly...

when measuring the voltage.... where did you put the red wire and the black wire to get the reading?

Pics can really help...

A voltage drop across a switch that is tiny is OK... If it were zero, that would be... ideal.

when measuring the voltage at the starter... compared to the engine mount or engine block... 10v is kinda low... when the battery has 13v to offer...

Somebody had a similar challenge the other day... they brought some jumper cables along to temporarily allow for additional electrons to pass...

often master relays and starter relays will switch, but not deliver adequate power... See how old your are... age and hours...

relays or ‘contactors’ are just powered switches... ideally there would be 0V drops across them...

It is starting to look like your starter relay is showing some resistance/lower voltage coming out of it...

Do you have a POH, and the basic wiring diagram?  This can be helpful to really understand what you are seeing...

PP thoughts only, not a mechanic...

Best regards,

-a-

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Just because the solenoids make contact does not mean they are passing all the amps.   I am not a fan of metal can solenoids.  Could also be the brushes on the starter.  More a fan of B&C starters than skytec.

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Which Skytec starter do you have?  I had one that looked similar to the old Delco Remy starter that did a similar thing.  It only had 100 hours since install.  When I called Skytec they said they no longer used that starter for the Mooney’s.  They use the in-line starter now.  Once I installed the in-line starter I have had zero issues.  I also installed Bogert power cables this year.  If you order any make sure of your ground cable.  They sent a zero degree rotation and my C needed a 180 degree rotation for the ground wire.

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I just had this problem with my Mooney and finally tracked it down to a bad lug going to the starter solenoid. If you checked voltage on the input side if the starter relay voltage looked good until it was put under load then it fell off when you engaged the starter but if you checked the wire just above the lug the voltage was there.I have a buddy that had a kit to put lugs on and he recrimped mine and it is fine. Hope your problem is as cheap /simple to repair

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Talked to the mechanic and went through all the components of the system again. Starter solenoid was on its way out. Replaced it and did several start-ups with no issues and good voltage all the way to the starter.  Thank you all for the help. Cheers

 

(and some photos of the aircraft I forgot to include initially)

CC708E3F-0CE9-4A53-810F-3D2A00623511.jpeg

ACBB8B32-DC89-426C-838C-1CD51FA62718.jpeg

8B36EF52-CD6A-468B-97A8-47B9015988CD.jpeg

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  • 4 weeks later...
Great follow up DR! We have about four relay challenges this weekend...

One Bravo Master, One J starter, and yours... and Gary’s E he just reported above...

That’s a lot of relays getting worn... 

Best regards,

-a-

 

 

All these solenoid posts have me thinking a proactive swap is in order before our Big Trip West.

 

A fix of less than 100 bucks versus a surprise stay at a fuel stop will make the bride happier on our vacation trip.

 

Sent from my iPad using Tapatalk

 

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