Stihl FS85 problems

Discussion in 'Mechanic and Repair' started by Mikol, Dec 29, 2007.

  1. Mikol

    Mikol LawnSite Member
    Messages: 51

    While working at full speed ,all of sudden it shuts off. then when I go and try to start it back up, nothing.I have to let it sit for a couple of hours.then it works fine.can any one help. Thanks

    p.s I am no mechanic but it seems like something is causing it to flood.
  2. Ridin' Around

    Ridin' Around LawnSite Senior Member
    Messages: 266

    check for spark at the plug when it is dead, a good spark checker will eliminate that problem or point it out in a hurry. If the plug is not getting the signal to fire it would seem flooded. (wet plug) A bad coil can cool and fire again in some cases.
  3. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    I had a similar problem with my FS85 a couple of years ago. It was the ignition module that had gone bad and needed replacing.

    I would ask how old, now many hours of use, etc. But, electrical problem often don't follow usage patterns (e.g. some last forever, some don't last very long).
  4. LawnTamer

    LawnTamer LawnSite Gold Member
    Messages: 3,986

    I might also suspect a bad coil. I had a Maruyama edger that would do that, new coil fixed it right up.
    I am no mechanic though.
  5. AmsoilPower

    AmsoilPower LawnSite Senior Member
    Messages: 938

    I do believe Stihl has a lifetime warranty on their ignition modules. It is at least worth asking the dealership.
  6. Roger

    Roger LawnSite Fanatic
    Messages: 5,943

    I think you are correct. However, in the "heat of battle" when I wanted to back running, to think about working through the system to get a warranty payment was the last thing on my mind. By the time the approvals came through, I would have been a few says behind in my schedule, and getting the machine back running is critical.
  7. DavisLawn

    DavisLawn LawnSite Member
    Messages: 141

    pretty sure its a coil.
  8. Mikol

    Mikol LawnSite Member
    Messages: 51

    Thanks for all the Quick replies.I will check the coil out.
  9. J.J.

    J.J. LawnSite Member
    Messages: 24

    I have a stihl edger that did the same thing, and they replaced the coil and it works fine.
  10. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,586

    I have had some luck with using a volt meter to measure resistance on coil to tell when they are bad. It isn't perfect but seems to work. I measure them cold from the spark wire to cyclinder and it should have resistance. Then when it stops I measure it again and if bad the resistance is usually gone or open. Looking for spark isn't hard if you get into a dark garage.

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