Stihl MS201T Ignition Module

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KnuckleBusterAL

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An FYI for anyone else having this problem with Stihl ignition modules.
Not so much as a Question, but a heads up for anyone who is having problems with their Stihl MS201T
I run a Small engine shop and am a third generation small engine mechanic and have never run into one like this. Customer brought me his Stihl saw said it just quit and would not restart. Checked spark (None) Disconnected the module kill wire still no spark. Okay needs a new ignition module. Ordered one postal service ran over that one with fork truck. On to number 2. Installed proceeded to test spark (Nothing) Okay check mounting - good air gap - good continuity from coil mount to cylinder - good No spark. Decided must have a defective module. Number 3 Same results (No Spark) Spent sleepless nights asking myself what I was missing here. Checked all forums for possible other instances of these being bad. Finally I spoke to another long time Stihl Dealer. He knew of and had this happen to him. Stihl has and know they have an issue with the 1145 400 1303 ignition modules for these saws. So before you think you have done something wrong it may not be so. On to Coil number 4 has to be a good one out there. Right? and as pointed out from another forum the flywheel magnets are good.
 
So here it is 2 months after I posted the MS201T Ignition problems and this is how it went. The 3rd module was purchased from a local Stihl dealer. Installed it and it sparked for 3 pulls of the rope went intermittent and quit. Dealer says no refund on electrical parts. Talked to Stihl and they say it has to be looked at by the dealer to warranty the module. Okay. Take it to the dealer. Their mechanic change module AGAIN nothing, changed flywheel, nothing. Basically did everything I did and can't get spark. Sends it to Regional Stihl distributor they say they put it through their parts cleaner and they have spark. Great. But say it has 15 per cent compression leakage and needs a Cyl & piston for it to tune and run right. Then they send it back to my local dealer. I go pick it up get home test for spark, NOTHING. Call Regional Stihl, they say had spark there and if its sent back to them for the spark issue they are putting on a Cyl & piston. I've pretty much had it with Stihl, and it still comes down to their Ignition Modules are Junk. I have never had a repairable saw that I had to send back not running, but have no choice since Stihl will not help by supplying good parts.
 
So here it is 2 months after I posted the MS201T Ignition problems and this is how it went. The 3rd module was purchased from a local Stihl dealer. Installed it and it sparked for 3 pulls of the rope went intermittent and quit. Dealer says no refund on electrical parts. Talked to Stihl and they say it has to be looked at by the dealer to warranty the module. Okay. Take it to the dealer. Their mechanic change module AGAIN nothing, changed flywheel, nothing. Basically did everything I did and can't get spark. Sends it to Regional Stihl distributor they say they put it through their parts cleaner and they have spark. Great. But say it has 15 per cent compression leakage and needs a Cyl & piston for it to tune and run right. Then they send it back to my local dealer. I go pick it up get home test for spark, NOTHING. Call Regional Stihl, they say had spark there and if its sent back to them for the spark issue they are putting on a Cyl & piston. I've pretty much had it with Stihl, and it still comes down to their Ignition Modules are Junk. I have never had a repairable saw that I had to send back not running, but have no choice since Stihl will not help by supplying good parts.
I might be able to help---Shoot me a PM
 
Yes thanks to a fix that Giles had tried and worked for me also. If you would like to know send Giles or me a PM. Thanks
 
Yes thanks to a fix that Giles had tried and worked for me also. If you would like to know send Giles or me a PM. Thanks
Hello... I have 4- 201t's in my shop... All have the same problem... Intermittent/ no spark.. gone so far as swap modules from running saws... Same thing on all four.... Any help would be greatly appreciated... Thanks so much
 
Hello... I have 4- 201t's in my shop... All have the same problem... Intermittent/ no spark.. gone so far as swap modules from running saws... Same thing on all four.... Any help would be greatly appreciated... Thanks so much
Was able to get good spark back and stay good using a 192T module and modifying the plug lead to fit the 201T. Ran good for me but customer says thinks it's lacking power so uses it on the ground not up top. Stihl still says there is not a problem, but with so many having this problem I'd say they are wrong. I will not take in another 201T for repair since I was pretty much treated like crap by Stihl from Dealer to their corporate office. If you want full detail on the fix to get spark PM me I think I still have it so can copy and paste it in a reply. Have a great day
 
Thank you so much for the reply..... Yes I've even thought of that... I have a pile of junk 192 s... And I'm right along with you... Will not take a 201 in for repair.... These four saws we're taking in on trade... I personally don't feel that they are worth 120 dollar module... To try to get 250 out of them running..... I have run Stihl saws for over 40 years... I personally feel that after 2011 they all went to crap.... I thank you for your time... And thanks for the info
 
Thank you so much for the reply..... Yes I've even thought of that... I have a pile of junk 192 s... And I'm right along with you... Will not take a 201 in for repair.... These four saws we're taking in on trade... I personally don't feel that they are worth 120 dollar module... To try to get 250 out of them running..... I have run Stihl saws for over 40 years... I personally feel that after 2011 they all went to crap.... I thank you for your time... And thanks for the info

Send me a PM---Giles
 
i think i got lucky i have one of the frist non m tronic 201 it hasnt gone out yet and mine had the timing advanced
 
Thank you so much for the reply..... Yes I've even thought of that... I have a pile of junk 192 s... And I'm right along with you... Will not take a 201 in for repair.... These four saws we're taking in on trade... I personally don't feel that they are worth 120 dollar module... To try to get 250 out of them running..... I have run Stihl saws for over 40 years... I personally feel that after 2011 they all went to crap.... I thank you for your time... And thanks for the info
Agreed
 
I am about to trash this saw!!!!! Same problem as op. I replaced the coil and I dont understand why still no spark. Oh I get it, stihl doesn't work. Of all my saws 261 360 440 and ts420 ts500i fs100rx never had this kinda bs problem and ive delt with the dirty flywheel on the ts500i so its not that. Any advice would be appreciated or if anybody wants it, it will be in the rubbage bin. I knew I should have held out for a 200. Ill be damned if I buy a new one as I believe there all junk now. Why is it the oldest stihls I own are the most dependable? Although beatup and wore out they always work.
 
Is the problem saw a standard MS201 or is it an M-Tronic unit? I am the saw tech at a large VA Stihl shop and have never found a no-spark situation in a MS201 saw that was the fault of the module.
MS201TCM's (M-Tronic) saws can spark once or twice and have no spark if the diode assy on the carburetor fails. There is an easy test for the diode that is on Stihl I-Cademy site. The diode/switch is the OTHER electronic part on the carb- not the solenoid. Its easy and cheap to test and replace if nescessary.
M-Tronic is a solid system. It, like all systems, has occasional problems. These problems are more likely compounded by techs who haven't made the effort to learn proper test procedures before jumping to conclusions and replacing parts. Other than some leaky nozzles and 1 bad diode assy, I have NEVER found any failed M-Tronic components. I am not including old style "unlocked" modules in this list- they still had spark but could cause the saw to run too lean.
 
Everyone please bear in mind that my basic electronics background was very basic & ancient and a lot of things have been forgotten.

My first thought is the diode being for handling the counter emf spike from the solenoid.
So I was thinking that a failure would lead to damaged switching transistor in the coil/control unit.
But then you say that replacing the diode assy restores spark.

and some practical questions:
Is the diode internally damaged. shorted or open?
or
Or is it an external issue, perhaps dust & petroleum sets up a condition for arcing and a carbon track?
Cracked casing/potting/mounting compounds, or other places for funny unintended pathways for current?

What's the control module doing or sensing, that allows a diode swap to restore function.
Is it just an intermittent random change of electrical flow though a damaged diode assy ?
Does the control module have enough decision making capability to look for a "signature" of a proper diode assy
or is it just random electrical flow in the diode assy that cause the misfire?

That asked. Does the current that passes thorough said diode, get used in a series circuit with the high tension (spark) coil?
or are there separate parallel pathways?

I'm a mostly curious about this pathway stuff as it says something for how vigorous of a rope tug it will take to initialize the system.

-------
edit: I'm trying to ad a few missing words, to hopefully make this a bit more readable. Oftentimes it's tough to get my thoughts typed out, before they scroll through my brain.
 
Everyone please bear in mind that my basic electronics background was very basic & ancient and a lot of things have been forgotten.

My first thought is the diode being for handling the counter emf spike from the solenoid.
So I was thinking that a failure would lead to damaged switching transistor in the coil/control unit.
But then you say that replacing the diode assy restores spark.

and some practical questions:
Is the diode internally damaged. shorted or open?
Or is it an external issue, perhaps dust & petroleum sets up a condition for arcing and a carbon track?
Cracked casing/potting/mounting compounds, or other places for funny unintended pathways for current?

What's the control module doing or sensing, that allows a diode swap to restore function.
Is it just an intermittent random change of electrical flow though a damaged diode assy ?
Does the control module have enough decision making capability to look for a "signature" of a proper diode assy
or is it just random electrical flow in the diode assy that cause the misfire?

That asked. Does the current that passes thorough said diode, used in a series circuit with the high tension (spark) coil?
or are there separate pathways?

I'm a mostly curious about this pathway stuff as it says something for how vigorous of a rope tug it will take to initialize the system.

Something you might consider---
I am just a mechanic, and retired Tool&Die Maker with no electrical training but I have tested six of these ignition coils and this is what I found:

I set each defective ignition coil in my Lathe and spun two different flywheels with the coil mounted on my tool post--
Coil Reviving 001.JPG Coil Reviving 002.JPG Coil Reviving 003.JPG
Every coil was DEAD until 2,200 RPM, at that RPM each one had a blue spark that would jump app. 1/4".
Less then 2,200 RPM, spark would disappear.
 
Giles. That is much appreciated!
Any fat chance you've got access to other ignition coils????
I'd love to see some lamination/iron mods with before and after timing notes.
The tapered "tail" thing (and shape changes) would be interesting to see about.
https://www.arboristsite.com/commun...tion-timing-issues.231455/page-3#post-6486632
anecdotal tangent : Our lawnmower engines are said to have a low revs cutoff point of about 200 rpm
because of people, hand spinning the blade,when clearing a fouled deck or blade.
Yep, incidental "hand propping" led to a lot of personal injuries (& lawsuits).
So thus we now have to give a pretty good tug to initialize the ignition of our mowers.

2200rpm: The threshold rpm to reliably power & run the circuit.
Is it controlled by something like a zener diode, that bleeds off the charge until a certain input level is obtained and tips things over to a run condition.
Does the zener then get switched out of things?
Or do we just need to keep sufficient inflow/rotation to compensate for the zeners loss path?

And Yes, I'll have some questions about using tuned resonant circuits (filter or band pass stuff) thrown in the mix.

Or is the modern ignition equipped with some sort of crystal oscillator for a time/frequency base, to count spark pulses rather than a threshold voltage.
This would need some manner of processing power.
we already know that some of the ignition modules store some start counts, run times and throttle positions.
So we know the electronics are in place, just what are their capabilities?

This leads me off to the upper rev limiters. Are they threshold voltage things, perhaps a tuned resonance that bleeds to ground at a desired frequency?
Or to a retarded timing circuit.
Or with digital, a divide by "N" that give the faltering
sputter that we can mistake for rich carb tune/"four stroking"

I got loads of questions and thoughts on this stuff.
But I now lack the access to the hard goods.
so I'm stuck with pestering, you, folks.

A variable (preferred) or multi speed spindle, the ignition unit, matching flywheel.
Strobe light and degree wheel.
And the time to run the various run ups & and make notes.
Sounds so simple, to just read about it , eh.
But ask the people who have acquired them, what it takes.

Edit: I figure I'm derailing things with my questions about ignition design & operations.
If someone would like to start another thread for them, that would be great.
 
Giles. That is much appreciated!
Any fat chance you've got access to other ignition coils????
I'd love to see some lamination/iron mods with before and after timing notes.
The tapered "tail" thing (and shape changes) would be interesting to see about.
https://www.arboristsite.com/commun...tion-timing-issues.231455/page-3#post-6486632
anecdotal tangent : Our lawnmower engines are said to have a low revs cutoff point of about 200 rpm
because of people, hand spinning the blade,when clearing a fouled deck or blade.
Yep, incidental "hand propping" led to a lot of personal injuries (& lawsuits).
So thus we now have to give a pretty good tug to initialize the ignition of our mowers.

2200rpm: The threshold rpm to reliably power & run the circuit.
Is it controlled by something like a zener diode, that bleeds off the charge until a certain input level is obtained and tips things over to a run condition.
Does the zener then get switched out of things?
Or do we just need to keep sufficient inflow/rotation to compensate for the zeners loss path?

And Yes, I'll have some questions about using tuned resonant circuits (filter or band pass stuff) thrown in the mix.

Or is the modern ignition equipped with some sort of crystal oscillator for a time/frequency base, to count spark pulses rather than a threshold voltage.
This would need some manner of processing power.
we already know that some of the ignition modules store some start counts, run times and throttle positions.
So we know the electronics are in place, just what are their capabilities?

This leads me off to the upper rev limiters. Are they threshold voltage things, perhaps a tuned resonance that bleeds to ground at a desired frequency?
Or to a retarded timing circuit.
Or with digital, a divide by "N" that give the faltering
sputter that we can mistake for rich carb tune/"four stroking"

I got loads of questions and thoughts on this stuff.
But I now lack the access to the hard goods.
so I'm stuck with pestering, you, folks.

A variable (preferred) or multi speed spindle, the ignition unit, matching flywheel.
Strobe light and degree wheel.
And the time to run the various run ups & and make notes.
Sounds so simple, to just read about it , eh.
But ask the people who have acquired them, what it takes.

Some time ago, Someone on this site posted about spinning a crankshaft to "revive" a dead ignition coil.
After doing this with a few coils, I decided it would be much simpler to do this in my lathe.
I have revived a couple of Dolmar/Makita concrete saws coils that had set for a long time, they revived and are still working today---as far as I know.
In addition to these, I have tried it on other makes and some revived and some didn't.
Seems like they "go to sleep" if not used for a while?
I have worked on many small engines of all makes and have encountered more bad Stihl coils then any other.
 
Hmm. makes me think of reading about guys baking certain Lawn Boy & Suzuki ignitions.
Seems the general opinion was it driving moisture out.
Not sure what components the moisture hindered.
I don't recall if the temp & time was high enough to re-flow any solder joints. (ex, gaming consoles)

I've seen some reading about "re-forming" (old) capacitors with a limited re-powering and lowered voltage being slowly raised to normal operation levels.
I haven't a clue if that's applicable to your situation.
 

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