MS661 -- No Spark

[Tom82]

Now, we are getting somewhere. The lead to the plug boot, shows some minor scuffing......albiet it is running thru a plastic channel. I tested that lead from end to end, and it showed zero breakage/ zero resistance. The coil # = 1144 4700 C. The solenoid is black. I have both black and orange fuel filters.........
As to dealer service......thats a slippery slope in this area. The major Stihl dealer insists that the unit, any unit, must be brought to the store. That includes walking in with the part # for an air filter, for a 290.....very uncooperative service dept. I inquired as to the diagnostic charge, for checking the system on this 661, with the MDG-1. I was told it is not a possible service. "We won't plug in and test, and tell the customer what the data says....." Odd.

Any part# for the up-grade would be greatly appreciated. My crossed - fingers are now open to suggestions. Replacing the coil is the first, and fastest step to spark. I will remove and VOM test the wiring for resistance first. Thanks for your insight. Now, I know frustration is easily abated, with a few simple questions, and some humility.

So, in an electrical system an ohm test on a wire will tell you if the wire is broken, burnt open, excessive corrosion leading to high resistance, and if the terminal ends are connected to the wire properly. It will not always tell you if the outer layer/jacket of the wire is damaged which could lead to a short.

Same goes for the spark plug lead. I've had leads that pass visual inspection and ohm reading but, they were broken in a way that lead to inconsistent spark. There one minute, gone the next.

 

[Captain Bruce]

So, in an electrical system an ohm test on a wire will tell you if the wire is broken, burnt open, excessive corrosion leading to high resistance, and if the terminal ends are connected to the wire properly. It will not always tell you if the outer layer/jacket of the wire is damaged which could lead to a short.

Same goes for the spark plug lead. I've had leads that pass visual inspection and ohm reading but, they were broken in a way that lead to inconsistent spark. There one minute, gone the next.

Understood. I will inspect the wiring visually. There one minute, gone the next. Like a prom date.

 

[PogoInTheWoods]

Some light reading on various aspects of the M-tronic system as applied to different models across the board..., more or less. The MS661 M-tronic is fairly well documented. And from the description of your dealer, you'll probably know more about it than they do by the time you're finished reading.

 

[Tom82]

Understood. I will inspect the wiring visually. There one minute, gone the next. Like a prom date.

Attached is a picture of the repair kit model number. Again, this kit includes a coil with the latest version of mtronic software, a solenoid (solenoid has been manufactured differently which supposedly helps with life span and is less prone to failure), and fuel filter (tighter micron to reduce the chances of junk getting into the solenoid).

Hope this helps.

 

[PogoInTheWoods]

Thank you. (I wrote this earlier, got sidetracked and never sent it.)

The individual components required to upgrade a v1.x MS661C-M to a V.3.0 platform are 1144-400-4703, 4, or 5 for the control module (around $140); 0000-120-5104 for the white solenoid (around $80) - even though a black solenoid will still work with a v.3.0 ECM at around $40: and 0000-350-3518 for the 15 micron orange fuel pickup body/filter at around $6.

Would be interested in the part number for the $200 kit for future reference.

 

[Captain Bruce]

Some light reading on various aspects of the M-tronic system as applied to different models across the board..., more or less. The MS661 M-tronic is fairly well documented. And from the description of your dealer, you'll probably know more about it than they do by the time you're finished reading.

Thanks again Tom. The kit is unavailable in the area, from a dozen Stihl locations. Where can I buy this kit??
Backing into the rabbit hole, I can replace the black solenoid, wiring harness, and filter, and have ordered those parts.....as an experiment. As to the 4700 C coil......there is one available on e-Bay, with no lead??? I have never seen a 2-pce. ignition coil. Is the lead a simple plug and twist? I always felt the cable was a pressed, and sealed portion of the complete coil assembly....??

 

[Captain Bruce]

Some light reading on various aspects of the M-tronic system as applied to different models across the board..., more or less. The MS661 M-tronic is fairly well documented. And from the description of your dealer, you'll probably know more about it than they do by the time you're finished reading.

Thank You for this data. I'm big on printing and saving such information.........old school mechanic. Seems the repair kit with the V3 firmware, is N/A everywhere I look? Maybe its a service kit, for dealers who request it, ONLY?? I'd buy it in a heart-beat, if someone was willing to sell me one....Thanks again. BB

 

[Tom82]

Thanks again Tom. The kit is unavailable in the area, from a dozen Stihl locations. Where can I buy this kit??
Backing into the rabbit hole, I can replace the black solenoid, wiring harness, and filter, and have ordered those parts.....as an experiment. As to the 4700 C coil......there is one available on e-Bay, with no lead??? I have never seen a 2-pce. ignition coil. Is the lead a simple plug and twist? I always felt the cable was a pressed, and sealed portion of the complete coil assembly....??

The dealer can't order the kit for you? Are they no longer available from Stihl?

I would not buy a used 4700 coil, they are the worst of all the variations. Maybe a used 4701 coil? But, I wouldn't spend money on a 4700.

The spark plug lead just threads into the coil. There is a pin in the coil that stabs into the plug wire as it's threaded in.

 

[Captain Bruce]

https://************/threads/661-question-of-the-day.17631/page-6

 

[PogoInTheWoods]

The kit is not an off-the-shelf retail item and will need to be ordered from a regional distributor through a dealer with a clue. Bryan Equipment in Loveland, Oh. is the distributor for our region. Checked with my local dealer today out of curiosity and they show it as an active part number.

BTW, the forum police here don't like url's that reference 'competitive forums', hence the altered link in your last post.

 

[Captain Bruce]

The dealer can't order the kit for you? Are they no longer available from Stihl?

I would not buy a used 4700 coil, they are the worst of all the variations. Maybe a used 4701 coil? But, I wouldn't spend money on a 4700.

The spark plug lead just threads into the coil. There is a pin in the coil that stabs into the plug wire as it's threaded in.

I have "ordered" the kit, from the local Stihl dealership chain store. Crossed fingers I don't get told its special order = 6 - 8 weeks.

Thanks as always TOM82

 

[Captain Bruce]

Understood.

The kit is not an off-the-shelf retail item and will need to be ordered from a regional distributor through a dealer with a clue. Bryan Equipment in Loveland, Oh. is the distributor for our region. Checked with my local dealer today out of curiosity and they show it as an active part number.

BTW, the forum police here don't like url's that reference 'competitive forums', hence the altered link in your last post.

Understood. I was innocently keeping this thread active with any info. found. Since than, I have "ordered" the kit. I am all done with old part #'s, susbstitutions, etc.

 

[PogoInTheWoods]

What was your cost?

 

[Captain Bruce]

What was your cost?

$125, NIB, OEM, 2-yr. warranty

 

[PogoInTheWoods]

An honest dealer. Good for you.

And good luck.

 

[Captain Bruce]

An honest dealer. Good for you.

And good luck.

Thank YOU, for your time, consideration, and patience. I allowed my frustration with a lack of knowledge....all things M-tronic, to cloud my comments. Almost went off the rails. Thanks for putting me back on track.

 

[Captain Bruce]

Howdy Fellas: So, I have the kit in hand. Being the mechanical detective I am, I have to know what is wrong. I wonder? If I install the coil, and test for spark, and get it......is replacing the solenoid and pick-up crucial to the new control unit? If it ain't broke, etc. I really would like to avoid ripping out the entire wiring, carb, etc.....only to open up a can of worms......If this white solenoid is a real deal, I'll dive in. Just scratching my head before I head to the Bench........than there is the "re-set" process..........yikes.

 

[Tom82]

The early series of mtronic was problematic. You aren't replacing it just to troubleshoot, you are saving future headaches. Install the entire kit and be done with it. If you still have a no spark issue, it will be the wiring.

The latest version of software loaded in the new coil is much better and more desirable.

 

[rupedoggy]

It is my opinion (not Stihls) that when a better unit is made to replace an older one, ALL previous owners of the "crappy" units should get new ones at no charge.

 

[Tom82]

It is my opinion (not Stihls) that when a better unit is made to replace an older one, ALL previous owners of the "crappy" units should get new ones at no charge.

I believe they were swapping coils at no charge even in no longer under warranty but, not all dealers are the same. Also, I believe some dealers were swapping out broken case halves as well because of a known flaw.

I've bought and installed a few of the coil kits. It's not just the coil, it's the solenoid. The early solenoids were made differently and were more likely to fail from vibration or dirty fuel. The new solenoids seem to be more robust, they also now recommend the orange filter (higher micron count to reduce debris from getting in the solenoid.