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Interesting find troubleshooting MS261 C-M hard start issue

vdavidoff

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I do whatever I have to to get it restarted, which often means starting it in "start" or holding the throttle fully. Otherwise I'd just be pulling the cord all day with no results, when this happens.
 

Brewz

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I just had a 462 through that would run ok for a bit then bog down pig rich and stall out and not want to start again.
I found the hot/cold weather thing was the wrong way around from the factory and letting hot air into the carb box..... it doesn't snow here.
Switched that but problem still persisted.
Replaced the fuel solenoid and its perfect now.

Faulty fuel solenoid.
Yes its rare but it happens.
 

MustangMike

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Once they go rich Tony, they can take a LONG TIME to correct themselves. I had a 362 that took about 10 tanks and a 261 that took about 6 tanks (the 261 happened after I let someone else run the saw).

They both ran fine after they corrected, but it took a long time. Had to start them in the run position with the trigger pulled (easier with two people).
 

vdavidoff

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With the preface that I find these things take time to really know what has changed and what is just coincidence, I ran two tanks of canned fuel through the saw today and it was much improved. It still showed some signs of weirdness, but I don't know how much of that is something up with the saw, or maybe m-tronic (which I did not reset) still figuring stuff out.

Using the canned fuel the saw ran reliably and started as you'd expect, meaning primarily that I could start it in "run" after it was warm without doing anything other than pulling the starter.

However, for both tanks of gas, when I got on the throttle it'd bog for a split second before it'd spool up (which is unusual, but it did recover quickly) and it seemed to me like it was down on power. Just based on pitch of the motor I'd say it was running at 85% RPM of what it normally does at WOT, and it seemed to get bogged down easier than normal when cutting. But like I say, some or all of that might be m-tronic still adjusting. I am a little dubious that it'd take 6 tanks (or such) for it to get back to OK, but it's not like I actually understand what's in the firmware. I'm basing my experience with fuel mappings from 4 cycle automotive EFI which I know this is not.

The other thing is that after refueling, it did want to die when I started to get on the throttle after the first start, but I backed off the throttle, let it idle down, then slowly got back on it, and it seemed to figure it out and run as it had before being shut off.

It was another relatively cool day too, which I only mention because, that seems relevant.

But the short of it is that although I am still going to replace the solenoid since by all accounts that seems like a good idea (and I already ordered it), the canned fuel test seemed to be useful. We have two gas stations in town now, and I suspect the one I was going to might occasionally get some crappy gas, so I am going to start using the other place to see if maybe that's in the mix (so to speak). I'll likely run some of that gas through it before I get the solenoid, so I may be able to make some conclusion about the alternative gas, but yeah, lots of hand waving. As long as I get the saw working better/reliably, I'm good though.

Andy
 

Hobbylogger

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Same here as mustangmike. I have a 362c, suddenly quit one day. When I got home started back up ran good for a while and then died. So after some research I was determined that the coil was bad $107.00. The problem persisted although the run time got shorter. Then I upgraded to the white solenoid and orange filter, $45. Runs great now, stronger than ever. Then I found a bulletin, v3 kit comes with the coil, solenoid, and filter for $120.
Two good pieces of advice I got; if the dealership won’t sell you a kit ask for a district Rep. he’ll make it happen. And, check your warranty, these fall under an EPA reg. and stihl may have to fix it for you(mine wasn’t). Good luck
 

drf256

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Sounds like your solenoid. The canned gas helped it a bit, but I bet that’s your issue. The system was able to compensate better, but not perfectly, with the canned fuel.
 

RI Chevy

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I have a 261cm v1 with older fuel filter that is ported. I only run canned fuel or e-free fuel when I can get it. My oil mix is 32:1 - 36:1. I haven't had any issues as of yet. I clear out the carb after many cuts by piss revving it. I let it idle for about 5 seconds prior to shutting it down. Usually starts 1st pull every time when warm.
Maybe I'm just lucky.
 

Hobbylogger

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What’s pis revving.


Sent from my iPhone using Tapatalk
 

MustangMike

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I will add that when my 362 was in the middle of making back to normal, I was getting inpatient. I called (a well known dealer on this site) and was advised that if the saw is making progress to just let it keep making progress and NOT to do a reset, as then it may have to start all over (Note: We are talking about a ported saw).

All the stuff comes with pre set parameters that my not be optimum for your saw, your elevation, etc.
 

Wonkydonkey

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I hope you sort out your problem. I read your post about using canned fuel and it helped slightly.
How ever, I believe part of the piss reving was part of the reset process that @RI Chevy was talking about.
So once you get the saw running right. Find out how to properly reset it when you change the location, ie height above sealevel. Or when you run it out of fuel and it tries to compensate
 

MustangMike

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When you run it out of fuel the saw goes "rich" and will not idle long enough for you to do the reset process.
 

RI Chevy

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I tested that theory with mine Mike. I could not replicate it. I just choked it and it started and ran just fine.
 

vdavidoff

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I always found it a curious idea that a purported pro saw would stop working correctly if it ran out of fuel. I mean, I get that when you run the system dry, it has no prime, and m-tronic will have compensated for the lack of fuel as though it were a lean condition and have to figure things out again, etc, but it just seems like if a pro was using a saw, and it basically stopped working correctly if it ran out of fuel, they'd stop using that saw. But I know nothing about professional arborists, etc, I'm just a guy with a saw and some trees and some land. I would think if it became really difficult to use after running out of fuel, not just like, it takes a bit longer to start, that'd be a sign something else has gone weird, but I'm just speculating here.

I will say that when my saw was acting really poorly, I did run into a condition where I couldn't run it long enough to reset it. It'd run for about 30-45 seconds, hunting a lot but not sounding like it was going to die, then it'd just suddenly die. That happened after shutting the saw off with fuel still in the tank though, not only after running out of fuel.
 

MustangMike

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Trying to repeatedly start it with low fuel is usually when it happens, not just out of fuel.

When it happened to my 261, I had loaned it to a tree guy who was up in the tree. I kept telling the guy it was out of fuel, and he kept insisting it still had fuel and would not lower it to be refilled. Several times he started it and it died when he started using it.

I believe the repeated starts, and changing the angle the saw was in operation (resulting in a fuel starve) several times caused the problem.

I don't wish to repeat it again.
 

vdavidoff

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Have you vacuum and pressure tested the saw yet?

There is a chance the MT is acting odd because it’s trying to compensate for another problem.

I haven't yet. Is it safe to pressure and vacuum test without detaching the carb? My only concern about removing the carb is that I presume there'd be at least one gasket involved and I don't have any spare gaskets at this moment.
 
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