I'm new here, so everybody please excuse any ignorance...I have an almost new Stihl MS660 Magnum with a 25" rollomatic bar and yellow chain. The saw is about 2 years old. I bought it from a friend who bought 3 at one time for a business that didn't work out. It had literally never been used. We cranked it up for the first time when I bought it from him. I kept it in my garage until last week, when I took it out to cut down some medium sized trees behind my house which were threatening in stormy weather and provided some needed firewood. I had fired it up every couple of months while it sat - a little fuel, run it until it ran dry, then put it back up until needed. It ALWAYS cranked on the 2nd or 3rd pull, no matter what. Full choke - couple of pulls - it would fire - move it to run - pull once more and warp 20 immediately. Idled perfectly, etc... couldn't ask for better. Anyway, got it out, cut the one tree down - maybe 18" diameter. The saw ran like the beast it is and went thru it like the proverbial hot knife thru butter. Started to cut firewood length sections out of the felled trunk. It cut maybe a half a dozen flawlessly, then when I went to sit it down to re-position the rest to cut, it died. Would not crank back up for anything. Took it in the garage, checked all the obvious things - fuel filter - air filter - spark plug - plug wire, etc...nothing obviously wrong. It had cooled off in the meantime, so I cranked it and it fired up and idled perfectly again. Cut about 3 or 4 minutes with it and it just quit again. Now it will not crank any way any how...I am pretty good with engines in cars and trucks but have to confess that this is my first chainsaw fix it venture. I took the carb out, thinking maybe it was a bit of trash or whatever inside. It was as clean as a new dime internally. I still gently sparyed a little carb cleaner into the passages, and very gently blew everything out with compressed air then reassembled with a new OEM carb kit. Still no luck. So next, I took off the starter cover and took a look at the ignition module. Nothing obviously wrong there. All is so new it's not even dusty. Took the spark plug out again and got the idea to look for spark. Did it the way I've done it with cars for decades - plug in boot held next to grounded metal of saw and pulled the rope several times. Even got frustrated that maybe I wasn't seeing the spark and just got aggravated and held the plug in my fingers and pulled a couple of times -no spark whatsoever. So I thought...hmmmm, must be this ignition module breaking down internally when it gets hot? Got another one, from a running saw, exactly the same model and module part number, put it in and still the same!!!!! No spark, no start. I just can't figure this one out. It is getting clean, fresh properly mixed fuel. It is getting air. The carb. is perfect. Just no spark...??? What in the world could this be??? The wiring to the switch is perfect, I've looked at it a half a dozen times now...the fuel is premium 91 octane mixed with Stihl ultimate 2 cycle oil - fresh last week. It has literally run a total of about 30 minutes since brand new first being cranked. I know my way around an engine and have a half a dozen roll away tool boxes with top chests full of probably 40,000. bucks worth of tools collected over the last 35 years or so and this just has me floored. I really don't want to haul it up to the local Stihl dealer to let them charge me 200 bucks for replacing a connector or something. Can anybody out there lend a hand here? This thing is a quality piece of equipment, but now it's turned into a $1200. boat anchor...not to mention my wife standing there with that "yep, you really needed that thing" look - and the "you have all those tools for what?" look - HELP!!!
MS660 ignition problems
- Thread starter drsamm
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You say the wiring to the switch is perfect!Did you test the switch with an ohm meter? Did you try to get spark with the switch disconected?Also how do the magnetic poles on the flywheel look any blue color or cracks?Are you sure the ignition you swapped is the same was the air gap set? Is the flywheel key sheered?
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Yup I would double check the switch or its wire to the module.
BBB
Thanks for the quick replies! To answer the questions - no, I have not checked the switch itself with an ohmeter. I did not try getting spark with the switch disconnected - not exactly sure what that proceedure would be? Just unplug the wiring and try spinning it then? The replacement ignition module is exactly the same part number 1122-400-1314, so it's correct. I set the gap @ .008". The wiring itself is in perfect shape. The contact point where the wire that extends from the module to the switch is absolutely clean, as is the black wire that extends up to make the contact to kill the ignition when the switch is turned to "off". Checking all of this with a meter would be advisable, just to make double sure of continuity, so that's a good thought. The one that makes the most sense though, in regard to getting no spark, is the key being sheared off...can't imagine how that would have happened, (is this common?) but if the flywheel isn't spinning, it couldn't make much power, huh? I'm assuming that I can simply take the pull cord cover back off to expose the flywheel and try to spin it by hand and see if the piston is moving or not? Seems logical, but please correct me if there is a different or better way. If that winds up being the trouble, then it will be a matter of getting the flywheel off. I've seen several posts about what a pain in the rear this can be with any of these saws without a special puller. I've got many gear pullers, but I doubt seriously any of them would work with this. And I've seen the comments about loosening the flywheel nut out to the end of the threads and rapping it sharply with a hammer while holding the flywheel...that would scare the crapola out of me to try something like this with a saw this expensive! Is it advisable? My next move will be to check that flywheel, so please advise me what to watch out for and how to get it off without tearing up worse things, if it does wind up being a sheared key. Thanks again for the good ideas guys!!! I'll post the result of the flywheel check either later tonight or tomorrow afternoon...if any more thoughts pop up to anybody, please send them along...
Well, after Lone Wolf's suggestions, I got a little impatient and just had to go back down to the garage and take the pull cord cover off and take another look at the flywheel...I can pretty easily spin it by hand with the fins and can hear the compression coming out of the plug hole, and I can see the center of the crankshaft turning as the flywheel is moved. Wonder even if the key had gotten sheared off, if just the tightness of the retaining nut would still make the whole assembly turn, at least just with manually turning the flywheel by hand? But under the torque of pullling the pull cord would turn the crankshaft within the flywheel? Doesn't seem likely to me but maybe so. Again, I'm a real novice with this little motor...Will put a meter on the wiring sometime tomorrow to check continuity and try pulling the wiring off the switch and trying for spark. Otherwise, still dead in the water. I'm going to try to download some pics. of what I'm looking at so anybody advising can get an idea of the newness of this thing and the overall condition of the wiring and routing of it. Thanks again to Lone Wolf and BBB for the ideas already put forth!View attachment 210858View attachment 210859View attachment 210860View attachment 210861View attachment 210862
O.K. here's the latest on the MS660 ignition problem...took Lone Wolf's advice and did the following - checked wiring from ignition module to switch, both visually again and also with an ohm meter - wires are in perfect condition with no breaks or tears. Continuity thru both. Put the original module, which is basically new, back on and re-checked gap to 0.008". All good. The magnets in the flywheel will snatch the module contacts up against it when lined up, so they are really strong. Tried getting spark with the switch wires both connected and disconnected - no spark either way. The flywheel appears to be in equally excellent condition - no noticeable discoloration or cracks, etc..His last suggestion is that the flywheel key may be sheared off. When the pull cord housing is off the saw and the flywheel is exposed, I can turn it slowly by hand and hear the compression coming out of the spark plug hole, so this would indicate the piston is moving with the flywheel turning. I can also see the center of the crankshaft in the flywheel turning with it. Not sure if the pressure of the nut being tightened on the flywheel would be enough to turn everything by hand and make it appear as though the key was fine. Maybe the torque of the cord being sharply pulled is spinning the flywheel on the crankshaft, but no way to see it if it is and not sure if this is possible anyway. Although I can't imagine how or why it would do it, I thought he was on to something with the sheared key. (Is this a fairly common thing?) It made the most sense, given the condition of all else involved. I'm not sure where else to go with this one guys...I'm just flabergasted with it now - lost for what else to look for or at. It all actually seems pretty simple, just looking at it...Without taking the flywheel itself off for inspection of the inside of it and the key, I have no idea what else to try. From what I've seen in other posts with all Stihl saws, getting the flywheel off of one, without a special puller, is a real pain in the rear. I've got a drawer full of pullers, but I doubt seriously that any of them would work with this and that flywheel looks a little fragile to me. I've seen threads where it was suggested to loosen the crankshaft nut out to the end of the threads and rap it sharply with a hammer while holding the flywheel. Sounds like a not so good thing to try with something this expensive. Can anybody suggest this method of removing one as tried and true and that it wont tear up something else even worse? If somebody can suggest anything else to check, I'd sure appreciate it. Have no idea now...I tried to answer last night with some pics attached but it hasn't shown up yet on the thread? Don't know why, but maybe it will pop up and a visual of what I'm looking at may help with any other suggestions. Thanks for what's been offered up so far! HELP!!!
Not sure what your using to set air gap, but I had the same problem and set the air gap several times with a gauge and it wouldnt fire... Lonewolf told me to just set it with a business card so I tried it and sure enough I had spark... good luck
Hey,
Yes, I did pretty much the same thing and even went to the trouble of folding some sturdy paper I had on hand enough to make exactly .008" and very carefully set it and double checked it. Thank you for the advice, but I don't think this is my problem since it just quit from running fine the first and second times and it is so near to being brand new. And the module didn't move from it's brand new factory setting that first and second time it quit in the same 1/2 hour or so of cutting. Something has happened here that I just can't put my finger on and I'm just hoping some of you fellows with far more experience with these little engines can identify. Looks like Lone Wolf knows his stuff with these things, so I guess my next step it to remove the flywheel and see if something is wrong with the key or something on the wheel I cannot see from the outside. I'm just not real keen on trying to tap this thing off like some have suggested and I'm not going to give a small fortune for a puller just for this use...Just have no idea at this point...
Yes, I did pretty much the same thing and even went to the trouble of folding some sturdy paper I had on hand enough to make exactly .008" and very carefully set it and double checked it. Thank you for the advice, but I don't think this is my problem since it just quit from running fine the first and second times and it is so near to being brand new. And the module didn't move from it's brand new factory setting that first and second time it quit in the same 1/2 hour or so of cutting. Something has happened here that I just can't put my finger on and I'm just hoping some of you fellows with far more experience with these little engines can identify. Looks like Lone Wolf knows his stuff with these things, so I guess my next step it to remove the flywheel and see if something is wrong with the key or something on the wheel I cannot see from the outside. I'm just not real keen on trying to tap this thing off like some have suggested and I'm not going to give a small fortune for a puller just for this use...Just have no idea at this point...
Still NO spark!
O.K., at the end of my patience with this saw! Pulled the flywheel hoping the key had somehow been sheared and it wasn't. That would have answered everything about the spark. Cleaned the little bit of dust off of this nearly new flywheel from this 2 hour old saw and put it back on. Re checked the gap on the module, even opened it up a little bit from .008 to .0010 just to see if that might make some difference. It didn't. Pulled the plug wire apart to see if the coiled wire in the boot end that contacts the plug might be out of whack somehow. It wasn't. I'm just floored with this thing. There is absolutely nothing apparently wrong with it. Pulled the kill switch wire again just to quadruple check to see if it had anything to do with not getting fire. It didn't. I've checked everything you can check and it just won't fire. 'bout ready to sling it in the nearest lake. If it hadn't cost so much to start with, I'd consider it...So, I go on Craigslist this morning and bought a pair of saws from a guy closing his landscaping business, just so I would have something to cut with while I'm looking at my $1300. buck one sitting on the garage floor...an MS361 and an MS250. Both not used too much. A little dirty but had good compression and nothing broken. The guy couldn't get either to crank, so he just wanted to get rid of them. Gave him $135. for the pair, thinking if I had to rebuild the carbs. and fuel lines, etc., I'd still be way ahead. Got them home, cleaned the air filters - both really needed that. Changed the spark plugs, checked the fuel lines and tank filter, took the side covers off and just gave them a good blowing out with air and general cleaning and they both fired up to warp 20 on about the 3rd or 4th pull. Both idled like new and just ran perfectly...how can I get these two, probably each 3 or 4 years old, far more used than my "new" 660, do minor maintenance type work and cleanup on them and they fire right up??? Just don't know what else to do with this 660. It has me very disgusted with it at the moment...at least I have two saws that will actually run and cut something and have $67.50 in each one of them + the cost of two spark plugs, 1 bar nut and about 2 hrs. of clean up time...Anybody got any other ideas in regard to the 660 I'd like to empty my .45 into? Any suggestions would be appreciated! Don't want to waste the cost of the ammo right now...
O.K., at the end of my patience with this saw! Pulled the flywheel hoping the key had somehow been sheared and it wasn't. That would have answered everything about the spark. Cleaned the little bit of dust off of this nearly new flywheel from this 2 hour old saw and put it back on. Re checked the gap on the module, even opened it up a little bit from .008 to .0010 just to see if that might make some difference. It didn't. Pulled the plug wire apart to see if the coiled wire in the boot end that contacts the plug might be out of whack somehow. It wasn't. I'm just floored with this thing. There is absolutely nothing apparently wrong with it. Pulled the kill switch wire again just to quadruple check to see if it had anything to do with not getting fire. It didn't. I've checked everything you can check and it just won't fire. 'bout ready to sling it in the nearest lake. If it hadn't cost so much to start with, I'd consider it...So, I go on Craigslist this morning and bought a pair of saws from a guy closing his landscaping business, just so I would have something to cut with while I'm looking at my $1300. buck one sitting on the garage floor...an MS361 and an MS250. Both not used too much. A little dirty but had good compression and nothing broken. The guy couldn't get either to crank, so he just wanted to get rid of them. Gave him $135. for the pair, thinking if I had to rebuild the carbs. and fuel lines, etc., I'd still be way ahead. Got them home, cleaned the air filters - both really needed that. Changed the spark plugs, checked the fuel lines and tank filter, took the side covers off and just gave them a good blowing out with air and general cleaning and they both fired up to warp 20 on about the 3rd or 4th pull. Both idled like new and just ran perfectly...how can I get these two, probably each 3 or 4 years old, far more used than my "new" 660, do minor maintenance type work and cleanup on them and they fire right up??? Just don't know what else to do with this 660. It has me very disgusted with it at the moment...at least I have two saws that will actually run and cut something and have $67.50 in each one of them + the cost of two spark plugs, 1 bar nut and about 2 hrs. of clean up time...Anybody got any other ideas in regard to the 660 I'd like to empty my .45 into? Any suggestions would be appreciated! Don't want to waste the cost of the ammo right now...
Jkebxjunke
*Politically Incorrect*
could it be possible that you have 2 bad modules?... I am having a time with my 660 right now.. its a bear to start... then it will run fine... then leave it idle.. it will then die... but usually can crank it back up... now when it sits for about 5 to 15 min... it wont start... it wants to flood.... leave it sit for a few and it may try to fire .. sometimes... its like it has no spark...but then sometimes it runs.. right now I dont have a place to work on stuff... in the process of getting my shop done... but its never been a problem before... one thing I am going to have to do is replace the starter cord... who ever had it before only put about 16 inches on it.... so I have to 'drop start it" I have replaced the plug...
Not to be a pest, but you said you tested the spark plug, you might try a new one, you never know.
Maybe get someone to hang on to the plug wire,, cant hurt!!!!
You do have a good problem there!!!
Dont give up!!
BBB
Maybe get someone to hang on to the plug wire,, cant hurt!!!!
You do have a good problem there!!!
Dont give up!!
BBB
VA-Sawyer
Addicted to ArboristSite
Lets get back to basics with this problem.
Condition #1 Saw doesn't start.
Suspected cause is no spark.
Pulled plug and could not see spark at spark gap. ( Note: Some Electronic Ignition Modules can be ruined if fired without proper spark gap/no spark plug. Damage is caused by excess voltage arcing internally in module. ) I suggest using a spark gap with a clamp on ground lead for testing.
Someone then suggested a sheared flywheel key. Please note that if the flywheel magnet rotates past the Ignition Module at speed it should cause a spark even if the crankshaft isn't rotating. The saw won't start that way, but it will still produce a spark.
A good module with a good ground will produce a spark fom a rotating flywheel as long as the control wire going to the switch has a high enough resistance above ground. I have found that it takes about 100,000 ohms minimun between the module wire and ground to produce a good spark. Only use a high impedance meter for this check ( 10 Meg minimum ) as a cheaper meter can induce enough current to ruin the module. The unit should produce a spark if the module to switch wire is disconnected and isolated from ground.
Remember the control circuit is connected to ground only when you want to kill the spark. It is NOT like the car which uses a closed circuit when a spark is desired.
These electronic Ignition modules are pretty complicated and very sensetive to improper electrical conditions. They can be easily zapped by the wrong voltage in the wrong spot.
When properly installed and operated they are normally very reliable and tend to give better spark and better timing than the old points and coil systems.
See if your dealer has the ability to test both modules, If they are good then I suspect low resistance between the control lead and ground, probably through the switch.
A second cause could be a bad module ground as this presents a poor return path for the spark.
One last thing, I like to keep as much distance between the control wire and the HV spark plug lead as possible.
Good luck,
Rick
Condition #1 Saw doesn't start.
Suspected cause is no spark.
Pulled plug and could not see spark at spark gap. ( Note: Some Electronic Ignition Modules can be ruined if fired without proper spark gap/no spark plug. Damage is caused by excess voltage arcing internally in module. ) I suggest using a spark gap with a clamp on ground lead for testing.
Someone then suggested a sheared flywheel key. Please note that if the flywheel magnet rotates past the Ignition Module at speed it should cause a spark even if the crankshaft isn't rotating. The saw won't start that way, but it will still produce a spark.
A good module with a good ground will produce a spark fom a rotating flywheel as long as the control wire going to the switch has a high enough resistance above ground. I have found that it takes about 100,000 ohms minimun between the module wire and ground to produce a good spark. Only use a high impedance meter for this check ( 10 Meg minimum ) as a cheaper meter can induce enough current to ruin the module. The unit should produce a spark if the module to switch wire is disconnected and isolated from ground.
Remember the control circuit is connected to ground only when you want to kill the spark. It is NOT like the car which uses a closed circuit when a spark is desired.
These electronic Ignition modules are pretty complicated and very sensetive to improper electrical conditions. They can be easily zapped by the wrong voltage in the wrong spot.
When properly installed and operated they are normally very reliable and tend to give better spark and better timing than the old points and coil systems.
See if your dealer has the ability to test both modules, If they are good then I suspect low resistance between the control lead and ground, probably through the switch.
A second cause could be a bad module ground as this presents a poor return path for the spark.
One last thing, I like to keep as much distance between the control wire and the HV spark plug lead as possible.
Good luck,
Rick
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Hello VA-Sawyer,
Thank you for your obviously knowledgeable response...from the sound of your answer, you may just be a tad above my head with the electrical analysis. Your logical approach is good. A good suggestion to see if a dealer has a way to test the modules. There is a fairly large one pretty close to me, so I believe I'll take them over to see what they say. With the wiring being completely stock and not altered in any way and also being in pristine condition, I can't understand how or why it would be there. I have inspected both the power (green) wire and the ground or kill wire (black) twice already on both modules just to be positive that there were no breaks in them or cuts anywhere. Also checked them both with a meter for continuity. The original one is perfect and the other one is close to that, just a little dirty. When I tried the replacement module, I simply mounted it, gapped it and ran the wiring to the switch. I did nothing that would damage it. The flywheel too, appears as near perfect as you can get one, with no obvious defects. The magnets in it are strong enough to clamp the module pickup to it almost to the point that you can't pull it loose while adjusting the gap. I have set the gap at both .008 and .0010 just to see if it made a difference. No luck. In doing all of this diagnosis, it appears now that it has noticeably less compression??? This was both alarming and baffling since nothing whatever has been done mechanically. I took the muffler off as many suggest, just to take a look at the bore and it is shiny and clean, with no marks. So I put a compression testing guage on it and got a reading of about 90psi! What in the world now?? Maybe I'm not doing the compression check right, but it appears to me that it would be little to no different than checking a V8, which I've done several times. From what I read on these sites, it should be in the 150/160 range, particularly for such a new machine with no wear. I'm thinking that I'm going to pull the compression release assembly and see if something is wrong with it. It doesn't appear stuck or sticky, but who knows...So anyway, just something else to be baffled about with this thing. I will definitely follow some of your logic to see if I'm missing something. Thank you for taking your time to help me out!!
Thank you for your obviously knowledgeable response...from the sound of your answer, you may just be a tad above my head with the electrical analysis. Your logical approach is good. A good suggestion to see if a dealer has a way to test the modules. There is a fairly large one pretty close to me, so I believe I'll take them over to see what they say. With the wiring being completely stock and not altered in any way and also being in pristine condition, I can't understand how or why it would be there. I have inspected both the power (green) wire and the ground or kill wire (black) twice already on both modules just to be positive that there were no breaks in them or cuts anywhere. Also checked them both with a meter for continuity. The original one is perfect and the other one is close to that, just a little dirty. When I tried the replacement module, I simply mounted it, gapped it and ran the wiring to the switch. I did nothing that would damage it. The flywheel too, appears as near perfect as you can get one, with no obvious defects. The magnets in it are strong enough to clamp the module pickup to it almost to the point that you can't pull it loose while adjusting the gap. I have set the gap at both .008 and .0010 just to see if it made a difference. No luck. In doing all of this diagnosis, it appears now that it has noticeably less compression??? This was both alarming and baffling since nothing whatever has been done mechanically. I took the muffler off as many suggest, just to take a look at the bore and it is shiny and clean, with no marks. So I put a compression testing guage on it and got a reading of about 90psi! What in the world now?? Maybe I'm not doing the compression check right, but it appears to me that it would be little to no different than checking a V8, which I've done several times. From what I read on these sites, it should be in the 150/160 range, particularly for such a new machine with no wear. I'm thinking that I'm going to pull the compression release assembly and see if something is wrong with it. It doesn't appear stuck or sticky, but who knows...So anyway, just something else to be baffled about with this thing. I will definitely follow some of your logic to see if I'm missing something. Thank you for taking your time to help me out!!
GASoline71
Mr. Nice Guy
Holy cats! "Pair of Graphs" mang!
Gary
Gary
Bowtie
Gearhead
Did you try a new spark plug? They do take a crap on ya once in a while.
Bowtie
Gearhead
Ok. I suppose the flywheel might be a place to look towards. I had one quit on an 036, and an 046.
VA-Sawyer
Addicted to ArboristSite
If the compression felt good when you got it and it hasn't ran since, then I wouldn't worry about it right now. A squirt of fresh fuel mix in the carb throat should bring it back up.
You keep jumping to other things, no spark = no run. First get a spark, then if it won't start move on to the next item.
There is no POWER wire, it just runs from the module to the switch. A second wire runs from the switch to ground. Some modules are grounded at the mount and some have a second wire going to ground. If the control wire going to the switch can conduct to ground, even through a fairly high resistance, it won't produce a spark. That resistance can be through moisture, mud, or other debries.
Good troubleshooting is being able to seperate the fluff from the facts.
Rick
You keep jumping to other things, no spark = no run. First get a spark, then if it won't start move on to the next item.
There is no POWER wire, it just runs from the module to the switch. A second wire runs from the switch to ground. Some modules are grounded at the mount and some have a second wire going to ground. If the control wire going to the switch can conduct to ground, even through a fairly high resistance, it won't produce a spark. That resistance can be through moisture, mud, or other debries.
Good troubleshooting is being able to seperate the fluff from the facts.
Rick
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Make sure you dont have the switch in the off position when checking for spark. You need at least 100psi for a pop and normal is above 150 psi. The compression tester should have a schrader (tire) valve in the end or you will never get the correct reading. If your not able to get a better compression reading on it, your next step is to pull the muffler and see if the piston is scored with vertical lines. Ethanol gas, especially if its not fresh is causing alot of problems with these engines. Use a different spark plug. Good luck and let us know what you find.
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