MS261C wont start

[SteveSr]

Now, with a no spark, or more often, spark once, the harness gets replaced. Cheap enough and easy to do.

I spent a career in the electronics industry so know a considerable amount about wiring and connectors. So now I am wondering how wide spread wiring harness issues are on M-tronics tools. When you replace a harness and it fixes the issue (and doesn't come back) do you ever see any obvious issues with the old harness?

The issue that I am wondering about is all of the crimp and IDC connections in the harness. Normally these are done with specialized and calibrated (and high dollar) tooling. Under crimping will allow oxidation in to eventually open the circuit while over crimping will break wiring strands. I am wondering if Stihl (or their wiring vendor) has some quality issues.

My first job out of school was with Magnavox in the components engineering department. They actually constructed a home made and computerized temperature cycling test system to test connectors. At the time they had evaluated (and rejected) a connector system made by Molex. The previous summer the TV shop that I worked for while in school was paid by Sylvania to rework about 100 sets in a local motel due to a failed connector in the audio circuit. You guessed it! Sylvania had used the same Molex connector that Magnavox had rejected.

 

[stihl86]

I don't think its a problem. There aren't that many Mtronic problems to begin with. Most a normal problems that appear from use, misuse and just plain poor mechanic work. When someone has a problem with one, they immediately assume its the system and create more problem than they fix.

My point was, when a REAL Mtronic problem does appear, the harness is a good place to start.
A saw with big hrs, a saw that can rev up to 14000 rpm. with the harmonics that develope at the speed,
vibration is always a concern. When someone pulls off the connector wrong, it will surely destory the connection.
That's not the manufacturer's fault. The connections a extremely small also, for weight concerns.
A 1/0 connection would be better, but that brings up other problems LOL

But, you have a very valid point. It's a definite possibility. All the more reason to replace it.

 

[Tex68w]

Curious to see if the new harness solves the issue. I've had my 261C-M since 2017 and she starts right up every single time I pull her out, but I am extremely anal about cleaning my saws with a fine tooth comb after each use. I hate cleaning the house, garage, cars, and guns, but for some reason I find cleaning my saws therapeutic.

 

[Crispexx]

Thanks everyone for the help, currently I’m enjoying America’s birthday weekend and i won’t get back to it until Monday, but i spoke with the owner and gave him my(your) two cents and he’s going to get a wiring harness since it’s an inexpensive possible solution. But another update is after all that testing and tweaking and pulling apart i out the whole ting back together and she fired up the first pull. I let it idle on choke for about 20 seconds then fave the trigger a little tap and she died instantly, and I couldn’t get it to fire back up again. Flooded. Like what was said before I’m guessing (educated guessing with your help) the wires are messed up in the harness and when I wiggled everything and poked and prodded the connection was made enough to get her to roar but that was it. Once I get anymore news on anything I’ll update you!


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[wyk]

I had the same problem on my 241 recently. I removed the solenoid, cleaned it and the carb, put it back together with a new fuel filter, and did a few resets(the first 4 or 5 it wouldn't rev). Eventually she started to act normal again.
I've already forgotten the colour of the solenoid, though.

 

[SteveSr]

I had the same problem on my 241 recently. I removed the solenoid, cleaned it and the carb, put it back together with a new fuel filter, and did a few resets(the first 4 or 5 it wouldn't rev). Eventually she started to act normal again.
I've already forgotten the colour of the solenoid, though.

That sounds strange... I am wondering if a fault can cause the fuel numbers (calibration?) to get so far off that it won't run which would make it hard (or impossible to re calibrate)? Ignition module software bug?

I had a Toyota that would consistently do strange things if you started it up to move from the driveway to the garage (only run 30-60 seconds). The next day when you started it it would make all kinds of clicking (fuel injector) noises and buck like a bronco until it finally relearned how to run. This behavior was consistently repeatable and was apparently caused by an engine start without a full warmup. Toyota software issue?

 

[wyk]

According to, uh, Mustang Mike? If you let the saw run out of fuel too often, sometimes it just starts to act odd - flooding, idle, hard start, no rev etc. Sometimes it takes the saw a while to come back. It was easily 4 or 5 attempts at a reset before the thing started to idle like you expect an MTronic to idle at.
Also bear in mind this 241 is ported as well, but it had these issues before porting. It's always been a pain.

 

[Crispexx]

Well here's an update! I was able to get a hold of another couple MS216C's and i swapped the ignition modules on them and what do you know, the broken 261 started up and ran like a champ! the odd thing is i put the 'bad' module on the good saw and that saw fired up and ran just fine as well... so i have two saws that i switch ignition mods on and the both run great. I'm going to swap the ignition mods back and see if i can get the 'bad' saw to start and run again

 

[lone wolf]

Well here's an update! I was able to get a hold of another couple MS216C's and i swapped the ignition modules on them and what do you know, the broken 261 started up and ran like a champ! the odd thing is i put the 'bad' module on the good saw and that saw fired up and ran just fine as well... so i have two saws that i switch ignition mods on and the both run great. I'm going to swap the ignition mods back and see if i can get the 'bad' saw to start and run again

Gas in the heat is vapor locking maybe? Wait till its cool and re try.

 

[Crispexx]

Gas in the heat is vapor locking maybe? Wait till its cool and re try.

Not sure i follow, I got the 'broken' saw to run using an ignition module from another saw. I was also able to get the good saw to run using the 'broken' ignition module. So I have two running saws, just had to switch the ignition modules on them.

 

[lone wolf]

Not sure i follow, I got the 'broken' saw to run using an ignition module from another saw. I was also able to get the good saw to run using the 'broken' ignition module. So I have two running saws, just had to switch the ignition modules on them.

Oh mis understood. I didnt read all that.

 

[Crispexx]

Ok, update 2.0... Switched the ignition modules back to the original saws, started the 'broken' saw and it started and reved like normal. Tried to start it again not choked and it would cough but not start again. Put it on choke and it stayed running and did the 90 second reset, turned it off and tried to start it again w/o choke and no-go. started saw again and did another 90 second reset. still wont start not on choke. Saw will run on choke but will die as soon as you take it off choke and will not start w/o choke. So now it'll start on choke! better than before, but still not quite there.

 

[wyk]

I remember back when a $20 carb kit fixed all these issues...

 

[Crispexx]

Alright everyone, closure. After a lot of ripping apart, putting back together, lather, rinse and repeat, I got the saw running like a champ.

This little booger was ultimately the problem. Finally came across an MTronic saw with a bad ignition.


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[Overkill338]

I remember back when a $20 carb kit fixed all these issues...

Yes, and if you went up 1000 feet in altitude, you had to get the screwdriver and retune. Change octane of fuel, retune. Air filter gets dirty, retune. People raised hell about EFI in the 80's, but not any more.

I love the M-Tronic Stihls and Autotune Huskys. You old fuddy-duddys will catch up eventually lol