Ms261c no ignition

[sapponetta]

Hello. I'm the operations manager/mechanic for a commercial landscaping company. Have an ms261c that started for a split second and died. No ignition. Coil tests 25ohms. Did standard ignition coil testing procedures. Continuity on wiring is good. Crankcase checks. Brand new plug of course. Stihl dealer technician specifically told me that a faulty or failing fuel solenoid will not cut off ignition. I don't want to put a $150 coil on this saw and have it not start. I'm not an expert mechanic by any means. I'm just the guy at our shop who knows the most so maintenance and repairs to fleet and equipment typically fall on me. that knows the most.... Any help would be appreciated. I absolutely hate the mtronic. Never have an issue repairing any other 2 or 4 stroke engines.

 

[SteveSr]

A bad wiring harness will kill the ignition in an M-tronic saw. If the computer can't see the solenoid it can't control the fuel mix so kills the ignition.

 

[sapponetta]

A bad wiring harness will kill the ignition in an M-tronic saw. If the computer can't see the solenoid it can't control the fuel mix so kills the ignition.

I checked continuity on entire harness. Spoke with a tech at our Stihl dealer today and he said a bad solenoid will not kill ignition. I hate these saws. Never have trouble getting anything else running and starting easy. 99% of our problems are gummed up carbs. No spark with harness disconnected either btw. I have checked every component of this saw 3x. Baffled.

Flywheel and magnets are good too.

I guess I haven't checked for power thru the HT lead, but Ive never witnessed a Stihl coil or lead fail and I'd be a little surprised to see this one now. And like I said, I measured 25ohms across the new coil and the current coil on the dead saw.

 

[L34]

Ohms mean nothing on an electronic coil.
Could be a diode,transistor,etc problem within the coil.
On my 441c the coil not "seeing" the solenoid would kill spark.
Not so much a bad solenoid itself.

 

[Greg Poole]

My MS261c had no spark and it was the solenoid that caused it to have no spark. I replaced the original black solenoid with the newer white solenoid. (The recommended green solenoid was back ordered).
It fixed the no spark.
Also, use the newer orange fuel filter.

 

[Greg Poole]

In Canada, the repair kit #1140 007 1802 which includes the white solenoid and orange filter is cheaper than the green solenoid by itself! $21.99

 

[lone wolf]

In Canada, the repair kit #1140 007 1802 which includes the white solenoid and orange filter is cheaper than the green solenoid by itself! $21.99

Yup just replace the solenoid and take it from there.

 

[sapponetta]

Yup just replace the solenoid and take it from there.

I guess I'll try the solenoid update and go from there. I just hate buying parts without being 100%. Very tempted to convert this saw to standard. Only reason we have the mtronic was to replace a stolen saw.

 

[lone wolf]

I guess I'll try the solenoid update and go from there. I just hate buying parts without being 100%. Very tempted to convert this saw to standard. Only reason we have the mtronic was to replace a stolen saw.

That part will fit other saws, a must-have in stock now a day if you work on them buy 2.

 

[SteveSr]

No spark with harness disconnected either btw.

Did you read post #2?

I guess I haven't checked for power thru the HT lead, but Ive never witnessed a Stihl coil or lead fail and I'd be a little surprised to see this one now. And like I said, I measured 25ohms across the new coil and the current coil on the dead saw.

You need to specify what "coil" you are talking about. The solenoid "coil" or the ignition "coil"?

Where did you measure the 25 ohms from? What resistance do you measure at the wiring harness at the ignition coil with the wiring harness disconnected from the ignition coil?

 

[stihltech]

Ok, if you "hate these saws", you should not have them. But the truth is you need to learn how to fix these saws. After all, they have been out for at least 10 years, the technology for much longer.
I would definitely get the service kit as mentioned before. It is the place to start on an mtronic.
How old are these units? Are they used commercially? Makes a big difference.
Can the solenoid kill spark? Never say never. Depends on what failed.
New solenoid and still no spark? Now go for the coil (controller on an mtronic) and harness. From experience of many before you.
I am assuming you have checked piston, bearings vacuum and pressure test. Remember, it is just a saw with more fuel control. Do not let the "Oh my God it has a computer!" syndrome blind you.
Verify you have something to work with first. Just like any other saw (or small equipment).

 

[ZeroJunk]

Get the Stihl dealer to plug it in. Not good for a whole lot IMO, but it will tell you if you have no connection. Meaning the circuit is open somewhere. Or shorted.

 

[SteveSr]

Get the Stihl dealer to plug it in. Not good for a whole lot IMO, but it will tell you if you have no connection. Meaning the circuit is open somewhere. Or shorted.

So is there a diagnostic connector on the saw and if so, where is it located? Or does the Stihl tool just plug in between the ignition coil and the wiring harness.

 

[ZeroJunk]

So is there a diagnostic connector on the saw and if so, where is it located? Or does the Stihl tool just plug in between the ignition coil and the wiring harness.

It would be on the operators left more or less even with the carb. You have wires coming from the ignition, to the solenoid, through the diagnostic port and back. It is just a two prong plug. You have a cable that goes to the ignition for the plug, like a spark tester, and back. And, through the diagnostic tool. All things working properly it will tell you how many start attempts, how many starts.
More often than not it will tell you that it can't connect. Which means there is a problem in the electrical circuit.
Good news maybe if it means your saw isn't burnt up.
More often than not, broke wiring issues. From a drop and broken handle. Wiring grounded somewhere. Bad ignition module. Seen all of that.

So, it is not a magic wand by any stretch. Just narrows it down some.

 

[SteveSr]

It would be on the operators left more or less even with the carb. You have wires coming from the ignition, to the solenoid, through the diagnostic port and back. It is just a two prong plug. You have a cable that goes to the ignition for the plug, like a spark tester, and back. And, through the diagnostic tool. All things working properly it will tell you how many start attempts, how many starts.

It is interesting that they use the HT spark lead. I wonder if they are testing the coil continuity or using it in some other way.

More often than not it will tell you that it can't connect. Which means there is a problem in the electrical circuit.
Good news maybe if it means your saw isn't burnt up.
More often than not, broke wiring issues. From a drop and broken handle. Wiring grounded somewhere. Bad ignition module. Seen all of that.

This is why I suggested that the OP measure the harness resistance at the ignition module which should show the solenoid resistance.

So what is the ratio of bad harnesses to bad ignition modules. From my electronics background I would guess that an ignition module failure is pretty rare unless there are internal software defects that can cause a module to kill itself. Properly designed hardware should be pretty reliable.

 

[sapponetta]

Did you read post #2?


You need to specify what "coil" you are talking about. The solenoid "coil" or the ignition "coil"?

Where did you measure the 25 ohms from? What resistance do you measure at the wiring harness at the ignition coil with the wiring harness disconnected from the i

That part will fit other saws, a must-have

Ok, if you "hate these saws", you should not have them. But the truth is you need to learn how to fix these saws. After all, they have been out for at least 10 years, the technology for much longer.
I would definitely get the service kit as mentioned before. It is the place to start on an mtronic.
How old are these units? Are they used commercially? Makes a big difference.
Can the solenoid kill spark? Never say never. Depends on what failed.
New solenoid and still no spark? Now go for the coil (controller on an mtronic) and harness. From experience of many before you.
I am assuming you have checked piston, bearings vacuum and pressure test. Remember, it is just a saw with more fuel control. Do not let the "Oh my God it has a computer!" syndrome blind you.
Verify you have something to work with first. Just like any other saw (or small equipment).

Commercial. I didn't buy the motronic saw. We have zero reliability or service issues with our other 10 Stihl saws. Or the 52 other pieces of equipment I maintain. Or our fleet. Or my 911 with custom fuel injection installed and calibrated by me. I understand what this silly system is doing and how it functions. It is purely a scheme to get more equipment to service.We cut from 10 degrees to 110 degrees. We have no issues with our older saws. If you read my first post I went thru the Stihl flow charts since I'm less familiar with this saw. Checked crankcase. I've ran thru diagnostics. Spent 20 minutes on the phone with a tech at my dealership. It's an early model btw. Stihl tech told me to replace the coil/control unit. Which goes against everything here. I don't even know how good our dealer service is because I maintain and repair everything.

It is interesting that they use the HT spark lead. I wonder if they are testing the coil continuity or using it in some other way.


This is why I suggested that the OP measure the harness resistance at the ignition module which should show the solenoid resistance.

So what is the ratio of bad harnesses to bad ignition modules. From my electronics background I would guess that an ignition module failure is pretty rare unless there are internal software defects that can cause a module to kill itself. Properly designed hardware should be pretty reliable.

I tested for continuity at every section of the harness. Did not check resistance of solenoid, could find no specs and had no known good part to test. and like I said, I actually forgot to check continuity thru the HT lead. I haven't messed with the saw in 2 days because I just moved on to less aggravating stuff, and that's saying a lot when modern diesel trucks are less aggravating.... i may be wrong, but I believe the diagnostic port is on the operators right where the harness runs to fueling control. Please correct me if I am wrong, but that is the only place to plug into this harness as far as I know. All this nonsense to trim down a carb setup too fat and have tons of hot start issues. Thanks Stihl! Like I said, this is just a way to drive more equipment to dealers for repairs and service and the result is hurt productivity for the people who depend on their equipment.

 

[ZeroJunk]

I have had one bad ignition module. One. But, I have maybe worked on only twenty of these where the problem was not obvious. Whole top handle broke off obvious, majority being MS201's. Other than that more often than not it is the solenoid. Followed by a broken wire, or wire pulled out of one of the connectors. Usually if it is the solenoid it will run, just not right. If the saw is made in such a way that the harness is routed through a groove in the magnesium a tiny bare place on the wiring will screw the pooch.
I'm not sure I have even worked on a 261 mTronic . But usually the wires come from the ignition module to a connector on the solenoid through a short jumper attached to the connector attached to the carb, which goes to another connector that fits in a slot on the carb housing, just in and out. Then to the test port covered by a little push in cover, and back to the ignition module. The test port is just a T off of the harness, more or less.
Any broken or pulled loose wire in any of that will foul the whole system. As well as shorted to the magnesium.
May not jump out at you with an ohm meter that is using a tiny amount of voltage.

This is my understanding of it, keeping in mind I have never been to a Stihl school of any sort. Just repaired several through trial and error.

 

[L34]

If it helps, my running 441c with black solenoid,the solenoid measured 75ohms.

 

[ZeroJunk]

I have rebuilt several old stereo receivers, mostly Pioneer SX series. They have test points for trouble shooting.

Seems like Stihl would have put test points on these saws, particularly the fuel injected ones.

A multi meter probe won't go in the connectors. So, you have to find a little piece of wire or something to stick in the hole. And, if you are holding it with your fingers you are also reading the resistance across your fingers which is real and could be anything.

 

[stihltech]

You have been given the tools here to get it running. Follow through and let us know.
Overall, these are very good units as far as through this shop.