Diagnosing a shower of sparks issue

[phxcobraz]

Couldn’t get the plane to start yesterday. The shower of sparks is not buzzing at all. But the starter is turning. 
I replaced it(easy swap) with a known working one from my mechanic and am getting the same issue. 
I have an ACS ignition switch, with off-right-left-both-start. It does NOT have the push in for SOS, like the original Bendix ignition switch. It’s been in here since I bought it and always worked. 
Anything further to check? It would seem since it’s wired in the same contacts as the starter, it should run but I’m not getting any buzzing. 
The switch on the SOS is working, flipping it disconnects the starter. 
My thought is the ignition switch is the culprit but the starter turning is throwing me off. 

[Shadrach]

With a Bendix ignition switch, the “push in” is for the starter not the SOS.
Is your SOS wired to the starter solenoid?  Are saying that you have a starter defeat switch (for hand propping) and with starter disabled the SOS is silent?

If the SOS bench checks ok and the ACS ignition switch engages the starter, then I would say that you have an issue with continuity to the SOS box. Try using a jumper to activate the SOS.

[phxcobraz]

17 minutes ago, Shadrach said:

With a Bendix ignition switch, the “push in” is for the starter not the SOS.
Is your SOS wired to the starter solenoid?  Are saying that you have a starter defeat switch (for hand propping) and with starter disabled the SOS is silent?

If the SOS bench checks ok and the ACS ignition switch engages the starter, then I would say that you have an issue with continuity to the SOS box. Try using a jumper to activate the SOS.

Yes SOS is wired to the starter solenoid at the ignition rather than having a separate key “step” like the bendix ignition does. 
the SOS has a “defeat” switch next to it under the panel and when that is engaged as if you wanted to hand prop, both the starter doesn’t engage and it buzzes when key goes to start position (different than when it is used to start, if that makes sense).

I tried jumping the 2 terminals(in-out) on the SOS and it tripped the starter circuit breaker.

My next step I’m considering running new wires from the ignition switch to the respective terminals on the SOS. 
I also have a new ignition switch on order, if I don’t need it I’ll return it but easier to have it ready than wait another 3 days when it’s determined the culprit. 

[jamesm]

Don't rule out an intermittent circuit breaker Ignition/Cigar lighter especially if the old big fat red/black button type. I had one go intermittent on me since connected to the cigarette lighter plug took me while to find.  since I immediately assumed it was poor connection in cigarette lighter  voltmeter connection.  turns out the CB had gone intermittent.

[Shadrach]

17 hours ago, phxcobraz said:

Yes SOS is wired to the starter solenoid at the ignition rather than having a separate key “step” like the bendix ignition does. 
the SOS has a “defeat” switch next to it under the panel and when that is engaged as if you wanted to hand prop, both the starter doesn’t engage and it buzzes when key goes to start position (different than when it is used to start, if that makes sense).

I tried jumping the 2 terminals(in-out) on the SOS and it tripped the starter circuit breaker.

My next step I’m considering running new wires from the ignition switch to the respective terminals on the SOS. 
I also have a new ignition switch on order, if I don’t need it I’ll return it but easier to have it ready than wait another 3 days when it’s determined the culprit. 

Just so you know, I went through this with 63 C a few weeks ago and I do not believe that one was wired in such a way that allowed the SOS to fire when the starter defeat switch was activated. I pointed out the issue but it was secondary to a mag p-lead/distributor cover problem, so everyone wanted to leave well enough alone.

[FlyingDude]

2 hours ago, phxcobraz said:

The shower of sparks is not buzzing at all.

I have one here if your SOS turns out to have soiled the bed.

[phxcobraz]

45 minutes ago, FlyingDude said:

I have one here if your SOS turns out to have soiled the bed.

Just put a replacement on today with the same symptoms so I’m not assuming 2 SOS are bad. 

[cliffy]

Just take a volt meter and trace backwards from the SOS to see where the electricity stops

This is not rocket science. Its only one wire. 

Is there 12 v power getting to the SOS? If not-

Go to the other end of that wire -

Is there12 v power getting to the other end of THAT wire? If not- if not continue as above and find where the power stops

Basic trouble shooting will save a lot of time and money instead of a parts cannon.

[Shadrach]

48 minutes ago, cliffy said:

Just take a volt meter and trace backwards from the SOS to see where the electricity stops

This is not rocket science. Its only one wire. 

Is there 12 v power getting to the SOS? If not-

Go to the other end of that wire -

Is there12 v power getting to the other end of THAT wire? If not- if not continue as above and find where the power stops

Basic trouble shooting will save a lot of time and money instead of a parts cannon.

Sorry to say this is revolutionary thinking in today’s maintenance world. 

[EricJ]

+1 to jumper power to the SoS and see if it buzzes.   If you have +12V on it and it's not buzzing, it's either bad or there's no ground.

If it does buzz, trace the power wire back to where it has 12V.

Maybe that's been done already, but it's the normal basic debugging approach.

[phxcobraz]

1 hour ago, EricJ said:

+1 to jumper power to the SoS and see if it buzzes.   If you have +12V on it and it's not buzzing, it's either bad or there's no ground.

If it does buzz, trace the power wire back to where it has 12V.

Maybe that's been done already, but it's the normal basic debugging approach.

It’s getting power. I don’t have a whole lot of tools at the airport, going back later today to jumper from the SOS to ignition on those 2 wires. I tried pulling a plug off the left mag and watching for spark against the cylinder and couldn’t see anything(it was bright out though), so I want to try that again with a second set of eyes while turning the starter. 

[outermarker]

you might disconnect the wire to the starter from the solenoid. This way the starter won't engage and you can listen for the SOS to buzz. If it doesn't buzz, open it and clean the points. You can also check the SOS with the engine timing. 

[phxcobraz]

Traced from battery to the ignition. Going into starter solenoid is 12V, coming out is 9V and then into the SOS and so on. Is there any resistor coming off the starter solenoid that would restrict to 9V? I would think it’s 12v. 
I jumped 12V direct to the SOS from the battery and I only hear the starter solonoid click. 
Voltage coming from the SOS goes into the ignition and nothing comes out. I swapped to the other ignition I have and same results. 
I do have spark at the cylinder when cranking the starter, confirmed with a plug on top. 

[phxcobraz]

6 hours ago, outermarker said:

you might disconnect the wire to the starter from the solenoid. This way the starter won't engage and you can listen for the SOS to buzz. If it doesn't buzz, open it and clean the points. You can also check the SOS with the engine timing. 

I tried just giving it 12V and only get a clicking at the starter solenoid, not any buzzing in the SOS.  

[EricJ]

9 hours ago, phxcobraz said:

I tried just giving it 12V and only get a clicking at the starter solenoid, not any buzzing in the SOS.  

Disconnect the SoS from the solenoid and then try it.   If the SoS buzzes with just 12V applied to it, then the SoS is fine.   If the relay is dragging the voltage down for some reason there may be an issue with the solenoid (especially since you said there's 9V coming out of it).

If you're getting spark, though, maybe it's working?   Seems odd.   I'd definitely try it with the SoS disconnected from everything else and then jump 12V to it.

[phxcobraz]

27 minutes ago, EricJ said:

Disconnect the SoS from the solenoid and then try it.   If the SoS buzzes with just 12V applied to it, then the SoS is fine.   If the relay is dragging the voltage down for some reason there may be an issue with the solenoid (especially since you said there's 9V coming out of it).

If you're getting spark, though, maybe it's working?   Seems odd.   I'd definitely try it with the SoS disconnected from everything else and then jump 12V to it.

That makes sense. And yes my suspicion is the relay to the SOS has gone bad and thus isn't allowing full voltage to go through.

My thought is since the SOS isn't engaging at crank, its firing but at 25TDC rather than at TDC which is where the SOS fires, thus why I still see spark but no light.

I can pull it out of the system and try it in isolation to be sure.

[phxcobraz]

Marked up the wiring diagram with voltage as I am seeing it, for anyone that might point out something obvious I am not seeing. I am pretty sure the starter solenoid is bad at one of the posts.

Looks like part #001464

 

[Kelpro999]

41 minutes ago, phxcobraz said:

I am pretty sure the starter solenoid is bad at one of the posts

Are we looking at two different voltages on one post at start solenoid?

[phxcobraz]

6 minutes ago, Kelpro999 said:

Are we looking at two different voltages on one post at start solenoid?

It has 3 posts, the input from the power relay, which is 12 at the starter solenoid post, it also reads 12 at the starter post, it reads 9 at the post handing off to the SOS and ignition switch. I confirmed on the wire going to the SOS also is 9V.

[Kelpro999]

Wire from north at batt. Terminal on ign. Switch  is low voltage. Trace towards master for cause. In diagram it passes by master but is fused directly off the buss bar. Should be system voltage. Buss bar is fed from start solenoid circuit wire#114. That you verified 12v. (3v drop is excessive) 

Edited May 2, 2024 by Kelpro999

[Shadrach]

Have you tried jumping 12v to the vibrator?

[phxcobraz]

6 minutes ago, Shadrach said:

Have you tried jumping 12v to the vibrator?

Yes, though I just left it in place and gave a jumper from the battery to it, it did not buzz and caused the starter solenoid to click. I will try Eric's comment of taking it out of the system completely and confirming it buzzes out of band. 

My next steps are to check a few more locations for 12V off the master switch circuit(as Kelpro999 inquired), test the SOS out of band, and if those all look good, I have access to a replacement Skytec solenoid to swap out. 

[outermarker]

Going from memory here...isn't there a difference in the type of solenoid for the starter and the one by the battery(power relay)?

Edited April 30, 2024 by outermarker

[Shadrach]

20 minutes ago, phxcobraz said:

Yes, though I just left it in place and gave a jumper from the battery to it, it did not buzz and caused the starter solenoid to click. I will try Eric's comment of taking it out of the system completely and confirming it buzzes out of band. 

My next steps are to check a few more locations for 12V off the master switch circuit(as Kelpro999 inquired), test the SOS out of band, and if those all look good, I have access to a replacement Skytec solenoid to swap out. 

I just read that the Vibrator only needs 8V to operate so I don’t think voltage is the problem

[phxcobraz]

18 minutes ago, outermarker said:

Going from memory here...isn't there a difference in the type of solenoid for the starter and the one by the battery(power relay)?

Yes they are separate(listed as power relay and starter solenoid in my image).