Stihl FS 460 C problems

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Hello, welcome aboard!

Stihl put their 'M-Tronic' electronic fuel control system into their large brush saws, oh some 4-5 years ago now. So they are essentially fuel injected rather than using a traditional carb with user adjustable jets.

Also, it is easy to miss in the light grey font, down at the bottom of every post, almost mixed in with users signature file - the date of each post. These were 3 years old now.

I run an FS 560, it was quite an adventure at first. If you have any questions on one of these saws, I could give one a try; have run brush-saws for many years.
 
Thanks for the comeback newforest. I knew it was an old thread, surprised to get a reply. This is one our brush saws at the ranch. It has worked well for a couple years now. It seems the spark is inconsistent. It acts like it wants to start when you first choke it, but it wont stay running. Nothing with choke off. Gone through the carb, new fuel, spark plug. Just got a copy of manual from thread, lending some help in diagnosing M-Tronic system. The microswitch on choke doesn't seem to have continuity off or on. its strange it has worked fine then all of a sudden won't start. From what I can tell, to replace fuel solenoid, you have to buy a whole carb. Looks like microswitch is included with wiring harness. Any help or suggestions would be appreciated. They had to take a simple system and complicate it with electronics.
 
There is also essentially a main sensor unit I believe, though this can also be called “The Solenoid” I think. Seems to me would be separate from ‘carb’ unit.

In my experience with early (1980s) vehicle fuel injection systems, the sensors the electronics depend on can be an early fail point as well.

The first step is usually to hook it up to the Stihl software and go from there. My saw was supposedly fixed by a simple ‘Factory Reset’ from within that software, but I suspect the dealer also had to replace something but wouldn’t tell me.

My understanding is that Stihl is quite a bit less guarded about lowly saw owners getting ahold of that software than Husqy is, but to make the connection you need a very expensive black box from Stihl. Whereas Husqy Auto-Tune units use a simple cable, but no one can get their software.
 
The microswitch on choke doesn't seem to have continuity off or on. its strange it has worked fine then all of a sudden won't start. From what I can tell, to replace fuel solenoid, you have to buy a whole carb. Looks like microswitch is included with wiring harness.

It would be good to have it checked with an ohm meter if the target values are reached. (all the cables) You have the service manual, it`s descriped in there how to do. The fuel solenoid valve can be replaced seperately, but a special screwdriver is needed to open that tiny screw. The inconsistend spark could come from a bad or broken electrical connection to the solenoid valve.
 
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