Hard / no start discussion - SOS Problems?

[33UM20C]

Looking for opinions on this problem I'm having. I've been working with @Shadrach on this issue and has been extremely helpful thus far with his wealth of knowledge, but it seems like we've exhausted all our options that we can think of. So I'm looking to MS to provide some out of the box thinking - or just prove our thinking.

I've got a 1963 M20C S/N 2465 with the IO-360 A1D. 

The problem: Extremely hard to start (hot or cold), seems to always start when I release the key back to 'Both' and kicks on RIGHT AWAY like its been trying to start the whole time.

All signs pointed to an ignition problem at startup because the plane ran fine once started, but even hot would not restart after a simple refuel stop.

So far in the search this is what has been done:

• Verified I have a SOS system in the plane
• Verified I can easily flood the carb when trying to start, so good fuel flow
• Boot pump works properly
• No containments in fuel lines
• Key ignition switch passed bench test & was cleaned and reassembled
• SOS system does enable when key is pressed and prop turns. I could not hear it over the prop at first
• SOS switch is ON
• SOS was jumped and buzzed as it should with all switches off
• With the starter disabled, spark plug lead removed and gapped above the block for grounding, no spark with SOS buzzing
• With the started engaged, prop turning, top plug lead disconnected and gapped to block, no spark was seen

With this info we assume that there is a problem going on between the wire from the SOS to the spark plug lead ends.. I.E the left magneto.

Does anyone have any ideas on this or simple ways to bench test the SOS? Is there something that could of been knocked out of place or put back together wrong during annual?

 

I've read through Don Maxwells article and tried to recreate what I could with my limited tools at my last visit to the airport.

 

A bit of background - I just bought this plane and it Immediately started happening after the Annual Inspection which was my Pre-buy. Previous owner in still in contact and says he never experienced this happening, mechanics said it started perfectly every time and I have no reason to not trust them as they are my local mechs with no connection to the previous owner.

Thanks everyone for your ideas!

[MikeOH]

Not sure why it would have been messed with at annual, but the fact you bench checked the ignition switch implies the wiring was removed.  Any chance the ignition switch wiring was hooked up wrong when it was reinstalled?  It seems like the mag is being inadvertently grounded while you are cranking; an mis-wired switch might well cause that.

[Hank]

6 hours ago, 33UM20C said:

I've got a 1963 M20C S/N 2465 with the IO-360 A1D. 

The problem: Extremely hard to start (hot or cold), seems to always start when I release the key back to 'Both' and kicks on RIGHT AWAY like its been trying to start the whole time.

The engine starting when the key is released is classic sign of a bad left magneto. Either the mag is bad, the switch is bad, or the left magneto wiring is bad.

I'd start by testing the left magneto.

[Shadrach]

Interesting tidbit about the OP’s set up - The first thing I did when I started troubleshooting the issue was to determine type of starting system. It was clearly an SOS setup. I engaged the key in the start position but no buzz from the vibrator. I bumped the starter by pushing the key but left it at that. Given the OP reported that engine only starts when the key is returned to both, I assumed there was a problem with the switch or the vibrator and therefore no spark through the retard points. OP is clearly mechanically inclined so I left him with some additional trouble shooting tasks for another day. 

He was able to get the vibrator to buzz with a jumper wire. He determined that the vibrator is wired to the starter (a la Cessna twin). So the vibrator engages with the starter. However, he has no spark at the plugs. 

I am left thinking that the retard breaker points are the issue.

What is odd to me is that someone installed a very expensive “push to start” Bendix switch (currently >$700) and didn’t bother to use the start position for the vibrator, The switch does not have the “push” label plate, but clearly requires a push to engage starter.

The system is equipped with a starter defeat switch under the cowl for hand propping. 

Switch setup aside, this looks to me like the the retard breaker is either not being energized or is not discharging. What the OP is trying to determine is if something aft of the mag could be causing this. He did verify that the vibrator lead is seated in the left mag.

@N201MKTurbo your input would be welcomed!

[33UM20C]

11 hours ago, MikeOH said:

Not sure why it would have been messed with at annual, but the fact you bench checked the ignition switch implies the wiring was removed.  Any chance the ignition switch wiring was hooked up wrong when it was reinstalled?  It seems like the mag is being inadvertently grounded while you are cranking; an mis-wired switch might well cause that.

I don't thin so, I made a map of the wires and labeled them etc. etc., But I never even took them off in the end. I just removed the back plate upside down and reinstalled the same way. Tested again and had the same results 

[N201MKTurbo]

I had this happen on my old M20F. It did exactly what you said. The only way I could start it was to get it cranking and then let go of the key. It would usually start doing that.

It turned out to be the wire in the mag that went from the retard P-lead to the retard points. It was touching the case and wore through the insulation and shorted the retard breaker. 
 

The switch connects the main and retard P-leads together when you push the key in. With the shorted wire, that shorts out both points, killing the mag.

When you release the key, it disconnects the two P-leads from each other and lets the mag work normally. If it is going fast enough, it will make a spark and you are off and running.

[N201MKTurbo]

Strangely, this happened to me on Don Maxwells ramp. I was looking at my current Mooney. I talked to Don on the phone, but he never came out. It was a Sunday afternoon. He didn’t have any thing to add. I pulled the P-lead cover off the mag to look at the points and found the shorted wire. I just pulled the spade terminal off the points and rotated it 180 degrees which pulled the wire away from the case. It worked fine after that. 

[N201MKTurbo]

FWIW, if the retard points have worn to where they aren’t opening, that would cause the same symptoms. Either way the solution is under the point cover. It is just 4 screws that are easy to get to.

[33UM20C]

6 minutes ago, N201MKTurbo said:

FWIW, if the retard points have worn to where they aren’t opening, that would cause the same symptoms. Either way the solution is under the point cover. It is just 4 screws that are easy to get to.

Amazing information. My mechanic said he had a VERY similar thing happen to him on a piper Aztec.  But you explained it in simpler terms for me.

Going to look into this tomorrow thanks!!

[Shadrach]

Just to close the loop on this one.  The SOS P-lead was not was not making contact with the terminal.  It was fully seated in the cover housing but it was obvious that contact was not being made (could not feel the contact spring when pushing the lead in).  The IA removed the cover and made an adjustment to the retard terminal contact which had no witness mark indicating that the retard P-lead had ever touched it. I want to say the gap between the lead and the contact was ~.25".  Points looked good (not shocking given the likelihood that they've never once fired).   Cover replaced, P-lead installed and the engine fired off normally in 3 blades without having to release the key.. No issues since.

These are newly manufactured Bendix mags that have been in service less than 250hrs and ~3 years. Fastener were still covered in factory torque seal. This was an QC issue.Airplane is clean and well maintained. I am surprised that it made it through at least two annuals and a pre-buy like this.  Aircraft owner raised the issue with others familiar with the plane and was told by all involved that they had never had a problem. 

[Echo]

I love a happy ending

[Littleman749667]

Ironically I'm having the same exact problem too. When I first start the airplane it would normally start just fine but when I want to get fuel and start it back up again it would rarely start. I did get a new starter right before I bought the airplane and I'm thinking maybe something got disconnected or something like that. 

But in a nutshell I'm probably going to get it looked at pretty soon and we shall see if it's just a minor little connector not connecting.

[Matthew P]

You could install a Surefly Electronic Magneto to get rid of the SOS and not have to worry about it.

 

[Ragsf15e]

51 minutes ago, Littleman749667 said:

Ironically I'm having the same exact problem too. When I first start the airplane it would normally start just fine but when I want to get fuel and start it back up again it would rarely start. I did get a new starter right before I bought the airplane and I'm thinking maybe something got disconnected or something like that. 

But in a nutshell I'm probably going to get it looked at pretty soon and we shall see if it's just a minor little connector not connecting.

Since you have an E, I’ll throw this out there (but we have plenty of threads on it already)… is it specifically “hot” starts your airplane struggles with?  If so, what is your hot start technique?

There are lots of ideas and techniques, but I personally will use my hot start technique anytime the airplane has already been run that day - ie, taxi to fuel, shutdown, restart = hot start technique.

Injected airplane engines are notorious for being finicky to start when “hot”.  They will start just fine, but may need a different technique than the first start of the day.

Edited May 2 by Ragsf15e

[33UM20C]

UPDATE - FIXED

Apologies this took so long to be posted I completely forgot to to so.

 

The Issue has been fixed. To quickly restate the issue, My 1963 Mooney M20C would refuse to start in ANY condition. It did not matter if it was 25 deg F or engine was flown and still hot - no start (for the most part)

Here is the original diag list:

• Verified I have a SOS system in the plane
• Verified I can easily flood the carb when trying to start, so good fuel flow
• Boot pump works properly
• No containments in fuel lines
• Key ignition switch passed bench test & was cleaned and reassembled
• SOS system does enable when key is pressed and prop turns. I could not hear it over the prop at first
• SOS switch is ON
• SOS was jumped and buzzed as it should with all switches off
• With the starter disabled, spark plug lead removed and gapped above the block for grounding, no spark with SOS buzzing
• With the started engaged, prop turning, top plug lead disconnected and gapped to block, no spark was seen

After this I did pull spark plugs and verified there was no spark using only the SOS.

With my legality running out on how much I should be taking off my plane I called an A&P for some help.

THE SOLUTION:

After a quick explanation to the mechanic it was obvious the problem was narrowed down to the left magneto that housed the retard circuit. 

We pulled the leads off the mag and the top cover. The problem was the retard lead had literally never touched the contact inside the mag. It was bent wrong from the factory. After bending up the little U contactor and putting everything back together the plane started up perfectly normal. It has done so for months now.

I will attach pictures of what I took but I don't have any of the specific U shaped metal, but its quite obvious where the lead touches.

What boggles my mind is the mags have 250 hours on them. Speaking to the old owner he recounts that he got used to holding the key just until the starter engaged... so he never grounded and mags on startup *facepalm* 

Anyway many thanks to all that helped figure this out (especially @Shadrachfor his wealth of info and referring me to the A&P who fixed it) and I hope this helps somebody in the future!

[Hank]

Note @33UM20C, if you're flooding your carb then younhave an O-360, not an IO-360. Yes, some people have swapped engines in their C models for the fuel injected IO-360 with more power, but it's almost prohibitively expensive to do so anymore.

Listing the right engine will get you more accurate help . . . . I don't know much about the IOs, but have been managing my C for seventeen years now. (God! Has it been that long???)

[Yetti]

On 4/29/2024 at 5:20 PM, Shadrach said:

Just to close the loop on this one.  The SOS P-lead was not was not making contact with the terminal.  It was fully seated in the cover housing but it was obvious that contact was not being made (could not feel the contact spring when pushing the lead in).  The IA removed the cover and made an adjustment to the retard terminal contact which had no witness mark indicating that the retard P-lead had ever touched it. I want to say the gap between the lead and the contact was ~.25".  Points looked good (not shocking given the likelihood that they've never once fired).   Cover replaced, P-lead installed and the engine fired off normally in 3 blades without having to release the key.. No issues since.

These are newly manufactured Bendix mags that have been in service less than 250hrs and ~3 years. Fastener were still covered in factory torque seal. This was an QC issue.Airplane is clean and well maintained. I am surprised that it made it through at least two annuals and a pre-buy like this.  Aircraft owner raised the issue with others familiar with the plane and was told by all involved that they had never had a problem. 

There are long and short P leads, sounds like someone used the wrong ones.    When I read the OP first description I was thinking P leads.

[Shadrach]

3 minutes ago, Yetti said:

There are long and short P leads, sounds like someone used the wrong ones.    When I read the OP first description I was thinking P leads.

Did not look that way to anyone involved including the local grey beard IA who was able to quickly remedy the problem utilizing the existing hardware. The most difficult part of the job was breaking the two heavily (overly) torque sealed, slotted screws loose with a stubby little screwdriver in a tight space.

[Yetti]

6 minutes ago, Shadrach said:

Did not look that way to anyone involved including the local grey beard IA who was able to quickly remedy the problem utilizing the existing hardware. The most difficult part of the job was breaking the two heavily (overly) torque sealed, slotted screws loose with a stubby little screwdriver in a tight space.

My IA suggested replacing the tops to the spark plug wires screws with allen head cap screws.   Seems like the mag itself could benefit from the same.   Snap on actually makes a tool for that.  snap on 020 screw driver

I found one in my stuff.   Thought about selling it on ebay.

[Shadrach]

10 minutes ago, Yetti said:

My IA suggested replacing the tops to the spark plug wires screws with allen head cap screws.   Seems like the mag itself could benefit from the same.   Snap on actually makes a tool for that.  snap on 020 screw driver

I found one in my stuff.   Thought about selling it on ebay.

I don’t know the thinking or utility behind using slotted screws for most applications. I’m used to it working on vintage British motorcycles, but almost always swapped them out for Allen or Phillips unless keeping the bike all original is a concern. 
This was supposedly a new mag with just 2XXhrs. Why they’re  still being built with slotted, cheese head, machine screws I cannot say.

[Hank]

3 hours ago, Shadrach said:

1This was supposedly a new mag with just 2XXhrs. Why they’re  still being built with slotted, cheese head, machine screws I cannot say.

1. They are plentiful
2. They are cheap
3. They are on the approved parts list
4. The FAA would approve a change to the parts list in only a decade or so, after multiple years' gross sales spent in testing to prove the new screw head works.