Stihl 021 quits

[Cedar Row]

Stihl 021 runs and cuts just fine, then after about 12 cuts in 8"dia. oak it quits. It will start again after a while, but quits almost immediately. Haven't checked anything yet. Any ideas?

 

[rd35]

The last time I had a saw behave like this I replaced the spark plug. Turns out that my plug had developed a crack in the porcelain that would not gap open until the plug warmed up and expanded. When this happened the spark would short circuit trough the crack gap and kill the saw. After a few moments of cooling the gap would close enough to make proper spark again, but after restart would quickly open up and short again.
A new spark plug fixed the problem for me. Not sure if this is what is causing your saw to die but it might be an easy thing to try.

 

[Cedar Row]

Hadn't thought of that; getting ready to do some checking on the saw, will start there. Thanks!

 

[nedsim]

I had the same problem with an 021 I fixed for a friend. It was the ignition module. As far as I know OEM modules are no longer available. Two sub $10 modules from ebay lasted less than an hour. The $35 module purchased from a dealer is still working after a couple years.

 

[lone wolf]

Th

I had the same problem with an 021 I fixed for a friend. It was the ignition module. As far as I know OEM modules are no longer available. Two sub $10 modules from ebay lasted less than an hour. The $35 module purchased from a dealer is still working after a couple years.

Thats what it sounds like.

 

[pioneerguy600]

Changing the sparkplug is the first and cheapest step, if that fixes it great but more often it is the module is failing. I have witnessed guys chasing their tails trying to work around failing modules. The way I check this problem is have the stuff necessary to test for spark immediately after the saw shuts down.Alligator clips on both ends of a short piece of wire and the sparkplug wrench at the ready as the test needs to be done immediately before the module cools down, if no spark then the module`s electronic spark control is degraded and no longer viable. It took me 3 months to convince my neighbor that it was his module gone bad, he is a stubborn Scott, he replaced most every other part on that saw and constantly argued it had spark when he tested it but the saw was always in a cooled down condition when he did the test.

 

[lone wolf]

Changing the sparkplug is the first and cheapest step, if that fixes it great but more often it is the module is failing. I have witnessed guys chasing their tails trying to work around failing modules. The way I check this problem is have the stuff necessary to test for spark immediately after the saw shuts down.Alligator clips on both ends of a short piece of wire and the sparkplug wrench at the ready as the test needs to be done immediately before the module cools down, if no spark then the module`s electronic spark control is degraded and no longer viable. It took me 3 months to convince my neighbor that it was his module gone bad, he is a stubborn Scott, he replaced most every other part on that saw and constantly argued it had spark when he tested it but the saw was always in a cooled down condition when he did the test.

Thats what happen when you do it their way.

 

[pioneerguy600]

Thats what happen when you do it their way.

Yea I did tell him right off that it needed a module but he wouldn`t have it, kept claiming it was a fuel problem and went ahead and bought new fule line,tank filter and a new OEM carb,gaskets and such, airfilter and messed with it every weekend, brought it over to me more than once but wouldn`t spend the $85. for a new module. I loaned him one of my 044`s just so he could get some wood cut but he is dead set on running Jonsered/Husqvarna saws, eventually he decided he would spend $45. for an aftermarket module, we put it in and the saw came alive again, still cutting most every weekend with it and is very proud he saved a few bucks.

 

[user 74409]

The coil used on Stihl 021 was also used on 023/025/MS210/MS230/MS250 models. There are many used OEM coils available on eBay at much lower price than new. Steer clear of MS210C/MS230C/MS250C with Easy2Start feature as the coil is different with different layout for mounting holes.

 

[david newbie]

Changing the sparkplug is the first and cheapest step, if that fixes it great but more often it is the module is failing. I have witnessed guys chasing their tails trying to work around failing modules. The way I check this problem is have the stuff necessary to test for spark immediately after the saw shuts down.Alligator clips on both ends of a short piece of wire and the sparkplug wrench at the ready as the test needs to be done immediately before the module cools down, if no spark then the module`s electronic spark control is degraded and no longer viable. It took me 3 months to convince my neighbor that it was his module gone bad, he is a stubborn Scott, he replaced most every other part on that saw and constantly argued it had spark when he tested it but the saw was always in a cooled down condition when he did the test.

I wonder if running the saw with an in line spark tester would serve that purpose?

 

[Cedar Row]

That sounds interesting! What do you think, pioneerguy? Guess you would have to cut wood to get the saw hot enough.

 

[pioneerguy600]

That sounds interesting! What do you think, pioneerguy? Guess you would have to cut wood to get the saw hot enough.

Sometimes the saw may need 10 to 15 mins to heat up enough to exhibit symptoms, the longer it is run with a failing module the shorter the warm up time seems to become. It is the heat that degrades the electronic chip in the module.

 

[pioneerguy600]

I wonder if running the saw with an in line spark tester would serve that purpose?

An inline spark tester should speed up the spark issue as it creates more resistance to the spark / high voltage discharge getting to ground.

 

[JG041]

The last time I had a saw behave like this I replaced the spark plug. Turns out that my plug had developed a crack in the porcelain that would not gap open until the plug warmed up and expanded. When this happened the spark would short circuit trough the crack gap and kill the saw. After a few moments of cooling the gap would close enough to make proper spark again, but after restart would quickly open up and short again.
A new spark plug fixed the problem for me. Not sure if this is what is causing your saw to die but it might be an easy thing to try.

Thank you for posting this. I had a similar problem with a McCulloch Power Mac 6. I replaced the spark plug and it runs fine now.

 

[ZeroJunk]

The coil used on Stihl 021 was also used on 023/025/MS210/MS230/MS250 models. There are many used OEM coils available on eBay at much lower price than new. Steer clear of MS210C/MS230C/MS250C with Easy2Start feature as the coil is different with different layout for mounting holes.

Some of them use 4 MM screws as well. A 5MM won't go through the slot in the lamination.

 

[HarleyT]

I would recommend taking off the muffler and taking a peek before doing anything.