farmhard
ArboristSite Operative
Based on the fact that the coils are grounded out to kill them I would say yes and it's the first thing I check, spinning on a drill with plug removed. See post #37
Ms261c no ignition
- Thread starter sapponetta
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farmhard
ArboristSite Operative
Actually I think you should have a look at what you wrote and edit the comment. It is a kick in the balls to the people on this site that are trying to help you and if so you should not be asking for advice.
Great. I would still update to the current fuel filter, air filter and fuel solenoid on that early version for better prevention issues in the future.
Yeah, been there done that. Sort of a last resort. But, you eventually run out of other explanations.
SteveSr
Addicted to ArboristSite
OP needs to try this and report back... and you (and all off the other armchair quarterbacks) need to pay attention!
SteveSr
Addicted to ArboristSite
Now that you have it running... disconnect the wiring harness at the coil and see how much spark you have and report back here.
sapponetta
ArboristSite Lurker
Yes that's how it works on a normal saw, and the motronic is no different. I knew this saw needed a coil, but I wanted to double check before I threw a $150 coil at a saw when I wasn't 100% confident in my understanding of motronic. there is so much bad information on the Internet, it totally threw me off on what should have been a straightforward repair.
So, just so I have it straight in my head
If you disconnect the plug from the ignition module it will fire, just like a non Mtronic. ??
Just that the solenoid won't work.
I sold my MS362 Mtronic or I would test it myself.
If you disconnect the plug from the ignition module it will fire, just like a non Mtronic. ??
Just that the solenoid won't work.
I sold my MS362 Mtronic or I would test it myself.
sapponetta
ArboristSite Lurker
Yes. The "ecm" is just sending a signal to the solenoid which is its duty cycle.
Obviously it has memory though...the Stihl diagnostic software can interpret everything you can extrapolate from a tach signal....I assume. Never seen the Stihl software. But I'm not sure what it could read besides rpm, Start attempts, duty cycle of solenoid, I guess engine position. If someone has more insight, or I am wrong, please share. I'm just making assumptions from looking at the saw. I don't see how the diagnostic softwares channel/pids can be grabbing engine performance info from any other source/input.
farmhard
ArboristSite Operative
Sent from my arm chair:
The coil chip grounds through the harness. The saw will not run with it disconnected HOWEVER
depending on how you test the coil "IF" the problem is in the wiring you should be able to get a different reading via a scope or led, a spark tester won't show squat.
I don't think anybody chimed in on the magnets yet either.
The coil that I replaced would not operate the solenoid. I got there when there was nothing else it could be.
Another coil related issue was the owner had replaced the top handle and harness on a MS201TC and when he put it back together he put the yellow wire under the screw that holds the connector in place instead of to ground.
Another coil related issue was the owner had replaced the top handle and harness on a MS201TC and when he put it back together he put the yellow wire under the screw that holds the connector in place instead of to ground.
SteveSr
Addicted to ArboristSite
So did you bother to verify that the original coil was actually bad by "back substitution"? Back substitution is that once you that you think that you have found the guilty component is to substitute it back into the system to see if it is still bad. I learned this about 45 years ago when replacing vacuum tubes in consumer electronics.
The point is that you have touched many other connected components in the wiring harness which could have been the real cause of the failure that you actually fixed without knowing it. Back substitution is the only way to prove that the original coil was really the root cause of the original failure.
SteveSr
Addicted to ArboristSite
WRONG!!! While you might get a spark or two, once the computer figures out that it can't see the solenoid it will kill the spark.
We are still waiting on the OP to perform this experiment.
I seem to be getting dumber as this thread goes on.
This is exactly what my 441c was doing.
Run for bout 3 seconds then lose spark as it didn't see solenoid.
So it was still getting fuel.
SteveSr
Addicted to ArboristSite
No disrespect intended but it would be extremely useful to everyone who has to work on these to have this information for future reference. Hopefully someone (or the OP) who has a working m-tronic could provide this information. Functionality may also be different between V1, V2, and V3 M-tronic systems so this should be tracked as well..
BTW, do you have access to any of Stihl's training info on m-tronic? A good theory of operation might be revealing.
SteveSr
Addicted to ArboristSite
I'll see what I can find. Certainly nothing coming in for repair, so I have the time.
Just to stir up more trouble, I don’t think anyone has mentioned the microswitch which is also in that circuit on the carb.
