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Discussion Starter · #1 ·
Is there a way to test a trigger coil? Can't find it by searching. Also, can the dealer test the ECM? I've tested the stator, checked all connections, tested wires for continuity, tried known-working coil and VR, replaced plugs, disassembled kill switch and cleaned the contacts (and tried with it unplugged), tested continuity on DESS. I'm at a loss (and running out of shop beer). I don't want to buy an ECM/DESS without knowing that's what my problem is. This a pull-start only sled. Any advice is welcome.
 

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Set the Multi Meter to Vdc and test for voltage while cranking over the engine.

Trigger coil is similar to a stator in that it generates current as the magneto flywheel turns next to it. So it's essentially the same test.
 

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Discussion Starter · #3 ·
Thanks Daag44. So if it produces any reading it's ok or is there a spec? I'll try in the morning.
 

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I think 0.2 to 0.35 Vdc. I corrected a mistake in previous reply and changed it to Vdc. I forgot the trigger coil has its own earth magnet.
 

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I use a volt meter for most of the electrical troubleshooting, so it shouldn't be a problem.
 

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I tried to have ecm checked dealer said they couldn't check it .only way was to put it on another machine

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The MPEM/ECM can be tested, but the tech needs to have training for it. I think it works better to keep it simple and break it down into the main components. Then you do the best you can to troubleshoot each part and hope for the best. If nothing comes out of it then you will need a spare MPEM from a part out which is sold at a reasonable price.

Even with a spare MPEM it can prove to be a challenge. There is a perfect example of this on DooTalk from last season that I can dig up later tonight to give you a good idea what to expect. The problem isn't identical, but close enough to draw from the experience. The owner had all the spare parts and swapped like you did, yet it was the biggest challenge I had ever seen. Fortunately the owner had every intention to win the battle and he did.

MPEM needs:

- Power to work.

- Output current to the ignition coils to generate spark.

- Input signal from the trigger coil to determine the timing of spark.

- Security Key (DESS)
 

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Discussion Starter · #9 ·
Well, I tested the trigger coils as per specs. The resistance checks out. I checked output on stator and TCs; voltage was all over the place which I attribute to my cheap multimeter. I removed the flywheel and the magnets were intact as was the key, and the key ways were normal. Visually, the stator looks clean with no melted or burned areas. There's a resistance test for the MPEM I found in the manual (thanks Jake) and that did not check out (OL). I think it's time to buy an MPEM/DESS and try that. If anyone has one, I have PayPal....

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What year manual, section and page did you find the resistance test?
 

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Discussion Starter · #11 ·
2005, Section 07 Electrical, pages 280-282. Mach489 sent me the manual yesterday after I posted.

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The resistance test is part of the overall MPEM troubleshooting.

The good news is a failed test is no indication of the MPEM itself.

All the test is doing is ensuring the MPEM is getting a good connection to Chassis Ground.

In other words the MPEM is probably fine and all you need is to find why the MPEM is not getting a good ground connection.
 

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MPEM tests while cranking over engine:

- Power = 3-5 Vdc from on Red/Blue and Black @ MPEM connector
- Trigger Coil = 0.2 - 0.35 Vdc on Blue/Yellow and White/Yellow
- Security Key (DESS) - Jump Black/Green and Black/White on DESS connector (harness side)
- Output to ignition coils = 225-275 Vdc on White/Blue and Black
 

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Discussion Starter · #14 ·
I'll try again with those specs. I may upgrade my multimeter so l can feel more confident in my findings.

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Just to be clear when testing the coils you need to be looking for an AC output. Output will change with the different resistance's of the coils tested and the rpm. Some AC voltage is good but be aware when the coil is subject to heat and vibration an internal open can form in the windings and that would be a failure. When a magnetic field passes over a coil of wire it produces and AC waveform. Other parts are necessary to create the DC.
 

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The spec for the Output to ignition coils seems way too high for cranking power, but I haven't done this in a long time. I would check if I had one. In any case there needs to be a measurable voltage to expect spark. By the time you find the problem with the Power/Ground or DESS then that part of the test won't even be an issue.
 

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Just to be clear when testing the coils you need to be looking for an AC output. Output will change with the different resistance's of the coils tested and the rpm. Some AC voltage is good but be aware when the coil is subject to heat and vibration an internal open can form in the windings and that would be a failure. When a magnetic field passes over a coil of wire it produces and AC waveform. Other parts are necessary to create the DC.
Just to clarify, I think you are referring to the stator when you mention testing the coils.
 

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Nope, This is right from the service manual pages listed. (282)
Trigger coils 160-480 ohms
voltage .150 to .350 Vac
 

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Ya, but that's for Fan Cooled engines which don't work the same. In post#2 I had made the same mistake by going off of memory of old sleds. Unfortunately there is other old stuff lingering in the memory that needs to be worked through :lol:
 

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It is amazing how much work is needed to work through the Shop Manuals. It's a constant battle. With enough misleading info and mistakes it teaches to be extra careful. Testing the MPEM ground with an ohm meter is perfect example. The better tool, and arguable the correct one to measure a ground connection is a volt meter. The same to test a fuse and relay. It is a mystery why an ohm meter is used for those things.
 
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