Stihl MS180C coil failures

[Rich B1]

I have a Stihl MS180C (actually, it is my wife’s saw). It is about 6 years old. So far, it has failed 3 coils.

The original lasted about 2 1/2 years. Saw started, was running fine warming up and just shut off, no spark.

2nd coil lasted about 2 1/2 years. The saw was getting a lot of use due to storm clean up. Same deal, was running and just shut off.

3rd coil lasted 2 1/2 months. We were going to clear up another tree from the June storm. She started the saw, it was running, started to bog down, then died. No sparknagain.

I have a gauge to set the coil/flywheel gap. I disconnect the kill switch. The plug was installed in my MS290 which actually started easy (rarity for that saw). So it comes down to yet another failed coil.

The saw runs well when it runs, we both like it since it is great for smaller work. But I am ready to toss this saw and buy something else.

Am I missing anything that could cause the coil to just fail? Flywheel magnets weak maybe? A path to ground I am missing?

 

[xyz123]

Are you replacing with OEM coils?

Aftermarket ones can be hit and miss. Even though I have great luck with afm ones myself.

 

[Rich B1]

OEM Stihl……

 

[dodge man]

I don’t really have any idea on why they keep failing. I can’t really think of anything off hand on a saw that would make them go bad, unless they come loss and screw up the gap. Try a cheap one off of Amazon.

 

[xyz123]

I just looked. OEM used even around 8-10 bucks on ebay. I bet dealer hits those pretty hard on mark up.

Only idea I can even think of. I know some stihl dealer techs in my group. One swears their spec plugs are required. I just use bosch, ngk, autolite here with no issues whatsoever.
But just in case your using some off the wall plug that maybe causing the issues?

 

[Rich B1]

I have been using Bosch plugs.

My wife likes the saw. Which is good as she helps with firewood duties.

We talked it over. “She” is going to buy a new saw. She wants this one for back up. So I ordered 2 fleaBay coils @ $12.00/ea. I am going to look at the parts diagram carefully and see if there are any insulators or spacers missing.

 

[Rich B1]

Not sure I found the smoking gun, but found something odd and interesting today.

Installed a new coil. In the process of setting the coil to flywheel gap, I found the top screw on the coil was tight, but the coil was not tight against the cylinder. The bottom screw would tighten the coil against the cylinder. Looking carefully at the old coil, I could see where the bottom slot on the coil had been tight, but not the top slot. The thread pitch was more coarse than any of my metric taps, so used a 5mm lock washer between the screw head and factory flat washer on both screws. That allowed both to firmly grip the coil.

I am guessing the coil vibrated and damaged itself. Time will tell.

BYW, the wife bought another saw this week. Another MS180C with easy start. She likes it. I used the old one today, ran fine.

 

[5030]

The newer Stihl's don't do much for me anymore. I have an MS that sits most of the time.