Hi everyone, I've got a Stihl chainsaw MS 261 C-M the has no spark and will not fire. Changed the plug checked the wires everything looks good. Do you think I have a bad coil? What is the best way to check the coil?
Thanks hope I get some replies??
Remove the starter cover and remove all wires from the coil
If it then has a spark then the wiring / stop switch is bad
If no spark then the coil is bad
I use an orange spark tester in the dark because the spark is quite faint on a lot of these engines.
Note a flash = a pulse is being sent down the pug wire
You still need a good plug to make the spark.
Thanks for the info!! I rechecked the coil again with a new spark plug and the same no spark. I then unhooked all the wires except the grnd wire and still no spark from the coil. I then put my meter on the switch wires there is a blk and a red and a grnd.I checked for continuity on the switch and I had it just on the red wire grounded to the ground wire. But nothing on the black wire which I presume is the feed wire? I then checked ohms on the coil and with the setting of 2000 I got 1.8 so what now? A new coil?? If so how much are they and does anybody have the correct part number for this coil to fit this saw? The numbers on the coil are1141 4701 B SMT 1745 does this help?
Thanks bertsmobile!
#4
StarTech
It is one these coils but your local should be able to narrow to correct one after he reads the reference service bulletins.
No I I just crank it over with the starter rope first and then I unhooked the wires from the coil and replaced the cover and pulled it again no spark either time with a new plug
The spark from a magneto is proportional to the speed the magnets pass the coil and the intensity of the magnetic field
At cranking speeds a lot of magnetos put out such a small spark they are just barely visible in a very dark room which is why I use the orange glowing in line spark testers.
The other reason is if the plug is bad & tracking down the electrode you will still see the dim flash . Even then some times I can only get a result by forcing the tester between the engine fins.
It is very easy to miss the flash as it is tiny at cranking speeds so before I pronounce one dead I run it on my high speed mains power drill at 2600 rpm which is around idle speed for most hand helds
As the magnet strength decreases so does the voltage produced and the time taken gets longer so the spark retards
Thus some times a week magneto can be used by reducing the air gap
Inside the coil is a Hall Effect trigger that has resistors & transistors in it so a direct Ω measurement is meaningless except for the secondary windings ( coil ground to plug cap
In 11 years only one chainsaw has a bad secondary but it does happen,
#11
StarTech
Remember this is a M-tronics controlled saw. Working on getting a troubleshooting guide when you don't have the diagnostic computer.
Ok I'm confused, if this is a M-tronics controlled saw then I can't check the coil like most coils? I think I need some more help here.
#15
StarTech
This should help some. Most of the information is dealer only and all is copyrighted. I actually not suppose to have any of this info on hand. Just know a good source for the info.
But here is a few extracts. Please carefully all the instructions especially section 5.4.2. The following info should be available the owner of the saw in the first place under the right to repair.
OK here's what I have done now! I bought a spark tester and hooked it up to the saw. I rechecked the gap on the flywheel with a feeler gauge and a business card and it is close to or even .10. Now got a socket on my drill made sure it was rotating the right way that the recoil goes. put the drill on low speed NO SPARK then I put it on high speed and I had SPARK!!! Wow!! put everything back together and tried starting it and it started. I let it run for a bit the took the brake off and ran it real hard for a while. Shut it off and tried to restart WON'T START. Put the tester back on and turned it over with the drill NO SPARK on low speed but I had SPARK on high speed. It still will not start!! So what do you think? I'm at a loss right now.
Ok I let the saw cool down for 2 - 3 hrs went out to the garage checked for spark with the drill on high speed had spark. put the recoil back on choked the saw pushed the decompression button down and had the brake on. It fired on the 3rd pull and ran?? I let it run on idle for some time then took the brake off and ran it almost wide open for a good while. I shut the saw down and tried to restart not choking and it never fired out of 10 or so pulls. I pulled the plug and it looks like there are some very faint white spots on the electrode? Is this normal for a new plug? Think the carb is messed up and running to lean? I'm open for any suggestions at this point.
#19
Fish
Yeah most drills don't turn the newer coils fast enough. I didn't pursue it because you said that you were using the pull starter.
Ok I let the saw cool down for 2 - 3 hrs went out to the garage checked for spark with the drill on high speed had spark. put the recoil back on choked the saw pushed the decompression button down and had the brake on. It fired on the 3rd pull and ran?? I let it run on idle for some time then took the brake off and ran it almost wide open for a good while. I shut the saw down and tried to restart not choking and it never fired out of 10 or so pulls. I pulled the plug and it looks like there are some very faint white spots on the electrode? Is this normal for a new plug? Think the carb is messed up and running to lean? I'm open for any suggestions at this point.
Well I thought either to lean or water. But still there's the problem of not starting when it is hot. I'm going to dump the fuel and put new fuel in. My wife's son-in law has had this saw for over a year and he said it wasn't running very good???? Imagine that!
Just about every new engine runs way way way too lean
Thus now days not uncommon to find engines that will not start unless the carb is choked, even when hot .
So next time try a couple of pulls with the choke on.
After 10 pulls that did not fire your plug should be wet.
Not soaking wet but wet just the same ,
Ok I got it started and let it run with the brake on for about 30 seconds. Then took the brake off and ran it wide open for about 90 seconds. Shut the saw off and tried to restart with the choke on after 10 to 15 pulls no start. Took the plug out and dry as a bone with the electrode being somewhat white? Ok maybe carb issues? I put a new fuel filter on the saw with fresh well mixed fuel so I know that is good. I will wait for your replys.
Sounds way too lean
Do not try & start the saw with the brake on
I am yet to find one that will happily start & warm up with the brake on as it puts a massive load on the engine
Imagine trying to start your car in gear with your foot on the brake
I am not familiar with this saw and can find bugger all in the way of tune up info
Does it have a butterfly carb ( high & low speed jets + throttle stop ) or a rotary valve carb ( just a throttle stop )
Yes they are very protective of how they do things I think I'm going to have to take it to the shop. My bet is the solenoid is not telling the carb what to do? Maybe that is the way to go. It's just like the new cars can't work on them unless you have a computer!!!!
It is a give and receive world. Most the Stihl information was donated to me. Just can't publicly post the complete manuals as they copyrighted and are dealer only access.
Beside I am a pack rat for service info I need to run my business. I only have 1 gigabyte of compressed Stihl info currently (still adding as I need info on in house repairs). And only have about 9 gigs overall of compressed info store on my G drive and about 3 gigs on my One Drive.
It like my accounting system with nearly 1 million part numbers with alternates linked so I can find parts at a better procured rate. Just loaded 9,120 Rotary part numbers, descriptions, and prices (cost and retail) this morning at 5:30 am. Now the process of cross referencing them begins. No wonder I use a bin system as I have over 2,200 different part numbers in stock. Plus I need to buy about $500 in storage boxes again so I can stack the parts out of the way but still be able to find them when needed.
If wasn't for my in house computer I would be lost in a mountain of paper manuals.
And this inventory has been reduce a lot as I got distributors now can deliver in one to two days. But still I need to reduce it even more especially as I approach retirement time.
