Stihl Mtronic, vapor lock, die on idle

[Jim Chance]

I recently bought two new saws, a MS 201CM V3 and an MS 261 CM V2. I have had trouble with both saws using filing station lead free/synthetic.  I am pretty sure a lot of the trouble was vapor lock. The bulb on the 201 would go dry and when I opened the gas tank I could see bubbles coming out of the fuel filter. I switched to premix from the hardware store (expensive!) and they run better, but not perfect. I still have trouble with the both saws dying when bleeping the throttle after cranking and they seem to flood sometimes. So I have a bunch of  questions. First, what are you supposed to do with a vapor locked mtronic saw? I can't put the choke on and pull to get the vapor out because the $%^#ing  computer is controlling the choke and I am not patient enough to just sit there? Second, do these saws flood? It sure acts like it floods when it is warm and running can fuel. Finally, is there some source that actual explains mtronic? Does it control just the mixture and timing or does it control the throttle plate too? Does it have an oxygen sensor and if not how does it "know" when the mixture is right? Does it have temperature and pressure sensors? What does the solenoid do? Does it adjust a needle in an orifice or something else?

[Ben Cut-wright]

I recently bought two new saws, a MS 201CM V3 and an MS 261 CM V2. I have had trouble with both saws using filing station lead free/synthetic.  I am pretty sure a lot of the trouble was vapor lock. The bulb on the 201 would go dry and when I opened the gas tank I could see bubbles coming out of the fuel filter. I switched to premix from the hardware store (expensive!) and they run better, but not perfect. I still have trouble with the both saws dying when bleeping the throttle after cranking and they seem to flood sometimes. So I have a bunch of  questions. First, what are you supposed to do with a vapor locked mtronic saw? I can't put the choke on and pull to get the vapor out because the $%^#ing  computer is controlling the choke and I am not patient enough to just sit there? Second, do these saws flood? It sure acts like it floods when it is warm and running can fuel. Finally, is there some source that actual explains mtronic? Does it control just the mixture and timing or does it control the throttle plate too? Does it have an oxygen sensor and if not how does it "know" when the mixture is right? Does it have temperature and pressure sensors? What does the solenoid do? Does it adjust a needle in an orifice or something else?

Several previous posts and now yours regarding "vapor lock" with little more than conjecture to cause that diagnosis.  You premise the fuel system is in vapor lock, then ask about "flooding".  An intimate knowledge of mtronic won't necessarily be of help if *everything is suspected faulty. "choking the vapor lock out" is a procedure I've never heard.

 
Two "recently purchased NEW saws" should have warranty. Good luck.

[doc henderson]

ben is right, this is a common thread.  take it to the dealer and when they tell you the M tronic is fine, run it and take it back if it acts up.  the dealer should be able to help you trouble shoot.  how old is the saw.  my 261 had to go in several times and tested ok until finally the dealer replaced the solenoid and it has run fine since.  the answer appears to be "no one".  no one seems to understand the M-tronic.  

[trapper]

I took my 261 cm to another dealer and they tested it and said nothing wrong.  Used it today and sometimes dosent start.  let it sit a while and it starts.  No problems with the 241cm.  Orginal dealer kept runing me around until it now is out of waranty.  Second dealer quoted me $75 for mtronic repair kit.  Includes fuel solenoid and fuel filter.  Echo is looking better all the time.

[doc henderson]

if the problem existed, it should still be under warranty  I guess it depends on how much your time is worth.

[Jim Chance]

Thanks for the comments. I am pretty sure they were vapor locking since (a) they were pushing bubbles out of the fuel filter, (b) had the same problem with two saws on same fuel, (c) bulb was dry on the one with bulb, and (d) changing fuel fixed problem on both saws. Flooding problem came after I switched fuel and no longer had vapor lock. Only used one saw much since then and flooding has cleared up. I am guessing the mtronics got confused and was enriching the mixture for a while? I do like to understand machines I work with and I don't understand mtronics. 

[kantuckid]

I've already posted r. e. my 241 C would start normally cold, then not idle well once warm, then very hard to re-start and balk badly once re-started.
 It's been sitting at my Stihl dealers over a month while they sell mowers for Biden bucks hand over fist. Truckload after load to a mom & pop store. He's (owner) a top tier Stihl mechanic just no time to get back on saws. He does pro logger Stihl saw work more than any other dealer near me. 
Mine came from a pawn shop next to new, ran great until it didn't. It's not a "what gas/mix do I use" issue. 

Anyone have experience with the Echo 501 P chainsaw? 

[Jim Chance]

I have both saws a while now and both are behaving pretty well. Initial problem was definitely bad gas. The mtronic does get confused sometimes and floods the saw. If they don't start in Delta with a couple of pulls  hold the throttle wide open and give it a few pulls. Running out of gas seems to confuse the controller.

[doc henderson]

I plan to never own another M-tronic saw.

[hedgerow]

I have both saws a while now and both are behaving pretty well. Initial problem was definitely bad gas. The mtronic does get confused sometimes and floods the saw. If they don't start in Delta with a couple of pulls  hold the throttle wide open and give it a few pulls. Running out of gas seems to confuse the controller.

I am coming up two years in June on my 261 CM and after I taught my crew of two not to run it out of fuel its been fine. If it gets ran out of fuel it can be a battle to get it started.  Starts good and runs good. Just bucked up three or four cord of hedge with it a couple Sundays ago. 

[SoldierP]

My 261CM still has starting problems of being hard to restart after being run hot and shut down.  The dealer said that the heat creates pressure in the tank and floods it. He suggested that I release pressure by opening the gas fill. I have done that and it seems to work. It shouldn't be necessary in a Stihl but maybe it is until they get a real fix, if ever.

[Real1shepherd]

Stihl has had a long infamous history of stupid engineering with their fill caps. If you haven't heard, read up on the past debacle with forest fire fighters and Stihl chainsaw gas caps. Fuel caps are such a simple thing.....but they managed to over-engineer it.

Not knocking their saws, just the fill cap build.

Kevin

[Spike60]

Granted I don't belong in a stihl thread cause I don't know what I'm talking about. But running saws dry all the time opens up the user to variables that can cause some restart problems on any saw. AT or Mtronic saws have the additional problem of the fuel settings changing as the saw tries to compensate for the tank running dry. Part of this depends on how often the carb "samples" to make an adjustment. Even older saws without the electronic stuff pose problems that would not be there if the user would just turn them off at the first sign of running out of fuel. One is that the fuel line is now empty and has to be refilled to get fuel up to the carb. Real easy on a saw with a primer, (and why I love them). On a saw with a long fuel line like a 372, you have to do that with the rope. Guy pulls it a couple times and nothing happens. Then puts the choke on. But the saw is warm. Maybe only needed the fast idle. Ooops, now I'm flooded. Maybe I'll swear at the saw and throw it. . Sequence isn't the same for every saw either. Some may want 2 pulls with the choke, but no more than that. Hot day, cold day. Possibilities are all over the place.

[axeman2021]

This past winter because of their insurance companies age requirements to run chainsaws and climb ropes up trees, I was learning to operate a John Deere cutter butcher.
This morning I hauled out my mean starting STHIL ms311 no fuel bulb or easy start, and my sweet STHIL ms261 with moronic fuel control.

The ms311 took a little care with choking and yanking it's never a quick starter, even the Stihl dealer guy flooded it when he tried starting it, but it always will start and get to cutting.

My ms261 with a choke and three yanks and off it went ready for full throttle Calb. and it was running smooth ready for some bucking work.

[kantuckid]

Once my dealer had re-set my MS241 Mtronic (MUST! be done on a computer program setup) it has run flawlessly ever since. It's not finicky towards fuel choices (I run 89 ethanol as Stihl says) choke use nor vapor lock and does it all OK. If I was the boy I used to be I'd sell it and get a non Mtronic 261, but that's not how life works, so I'm sticking with my lightweight yet sort of powerful saw. My larger issue is running a saw with a thinner kerf than I'd prefer. 
I've posted this before but the RK near me was selling the non-Mtronic saws far more than the puterized versions. 
My own dealer quit, they were a Mom & Pop business with him unable to hire & keep any help so they cashed in on the government handout money(truckloads of mowers, etc. per week until there were none to be had) then shut down as no mowers or saw parts. He was a master Stihl guy that loggers here used for their saws. Now loggers here are trying to find a Stihl dealer to sell them parts to work on their own saws and some dealers are stingy with what few parts they can get or have none to begin with. 
   

[ladylake]

 Stihl needs to get this mtonic controls saws fixed, I was out sawing for a customer on Sat who has a 362 Stihl that was using it all day.  Sometimes it would start on the first pull and the next time it would take 10 pulls.  Pure bs for any saw.  Steve

[beenthere]

Never have had that problem with my MS362 mtronic.. maybe something the fellow did wrong, and not the saw.  

A good feature with this saw is picking it up and just pulling to start. Works every time.

But we do know you do not like Stihl.  ;)

[barbender]

I don't think that every person that has an M-tronic issue is to blame, there have been issues with the fuel solenoids that I've read of. However, I know my Husky 562xp starts great in all conditions- if you follow the directions. Pull that choke out on a warm saw, it goes badly. If I engage the high idle, and not the compression release like the directions very specifically say, it fires right up. If I hadn't read the starting procedure (I usually don't) I could be a fairly experienced user that has a saw that won't start. But it would be my fault🤷‍♂️

[doc henderson]

I know my saw had a problem.  It was fixed with a newer solenoid.  The frustrating part was it was intermittent, and i think the dealer thought the same thing.  They know me well enough to know i was not blowing smoke.  I could have been doing it wrong.  but now I have a reliable saw and no issue unless I run it out of fuel.  The 661 was never fixed.  the same problem, I think.  it would run and start enough, and the test was "normal", so they kept telling me nothing was wrong.  the company denied there was a problem.  My dealer stood behind the saw and gave me full credit towards the 880 I have now.  

[ladylake]

Never have had that problem with my MS362 mtronic.. maybe something the fellow did wrong, and not the saw.  

A good feature with this saw is picking it up and just pulling to start. Works every time.

But we do know you do not like Stihl.  ;)

I dont like Stihls marketing, using thier once good name to sell low quality heavy under powered saws. Thier pro saws are OK but over priced.  Steve

[Whiplash1]

Same issue here with 261 version 2, runs fine till fill up(not run out of fuel) then no start or maybe idle then die. Bubbles out the filter. Running 90 no ethanol. Dealer said it's from winter blend fuel? Switch to another saw and till it's out of fuel the 261 is ready again. Anyone know for sure what the problem is?

[Jim Chance]

Once I got rid of the bad fuel causing vapor lock the saw has been pretty good. The Mtronic does get confused sometimes and floods the saw, but when it does it starts with few pulls with WOT.

[Jim Chance]

Same issue here with 261 version 2, runs fine till fill up(not run out of fuel) then no start or maybe idle then die. Bubbles out the filter. Running 90 no ethanol. Dealer said it's from winter blend fuel? Switch to another saw and till it's out of fuel the 261 is ready again. Anyone know for sure what the problem is?

Bubbles coming out of the filter means fuel is boiling. Sure sign of vapor lock. When you stop the saw the fuel sits and gets hot. Winter fuel boils easy.

[PoginyHill]

I recently had similar issues with my MS-261-CM, but did not notice bubbles out of the filter. Mine would often stall after filling up. Sometimes several times, and die when giving it throttle. Got progressively worse until it would essentially not run more than a few seconds at a time.
Then I cleaned out the fuel tank and the fuel filter. Couldn't believe the quantity of fine stuff in the tank and on the filter. Took a tank of gas for the computer to re-learn the fuel/air mixture, but runs like new now.

Might not be related to the issues mentioned in this thread, but I've learned my lesson.

[Magicman]

If you boil the gas in most any saw, it could be difficult to start.