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  1. #1

    Join Date
    Jul 2011
    Posts
    189
    Location
    Mississippi
    Mower
    John Deere

    Stihl MS460 wont start

    I have a MS 460 that will not start. It was not producing spark. Now it does intermittently with a different coil. The second coil is from another 460 that was running but cylinder went bad. Will not even try to start with carb cleaner. Done leakdown test also and had a small leak at the decompression valve. Cleaned and tightened it. It was after all of this when I noticed the intermittent spark. Before then I was getting a good blue spark. Tested with a spark tester.

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  3. #2

    Join Date
    Oct 2011
    Posts
    37
    Location
    Minnesota
    Mower
    Badboy

    intermittent spark usuall means the coil
    is bad try disconnecting the ground wire from the coil and check for spark again if it's better you have ground sometimes shorting in the wires leading to the kill switch

  4. #3

    Join Date
    Jul 2011
    Posts
    189
    Location
    Mississippi
    Mower
    John Deere

    Will do. Let you know tomorrow what I find thanks.

  5. #4

    Join Date
    Apr 2012
    Posts
    548
    Location
    Texas
    Mower
    Troy-Bilt Super Bronco

    Re: Stihl MS460 wont start

    Remove the wire to the coil and try checking for spark again. I had a honda lawnmower in my shop where the coil was completely dead and the diagnosis was to remove the wire to the coil to see if there was spark. If no spark then replace coil. You already replaced the coil but that doesn't mean the replacement is good. If after removing the coil grounding wire the spark does not improve I would try a known good coil. Maybe ask the nice fellows at the stihl shop if they have a test coil for a 460 they would let you try.

    The fact that you replaced the coil with another one and now you at least have intermittent tells you that either the coil grounding wire is intermittently grounding out or you have a weak coil. Trace that grounding wire to make sure it hasn't rubbed through to ground. Also, make sure the multi-function lever where the wire goes to is working properly.

  6. #5

    Join Date
    Apr 2012
    Posts
    548
    Location
    Texas
    Mower
    Troy-Bilt Super Bronco

    Re: Stihl MS460 wont start

    Got beat out again, this time by Briggs92

  7. #6

    Join Date
    Jul 2011
    Posts
    189
    Location
    Mississippi
    Mower
    John Deere

    That helped the spark. I haven't looked for the spot on the ground shorting out yet but I wanted to try getting it to fire. Still no go. Out of all the things I have worked on I have never had problems getting one to fire with carb cleaner. I have good compression, I have good spark now, and I add the fuel to the formula. I have pressed the decompression valve and tried it without pressing it. For some reason I can NOT get this thing to fire with fuel or carb cleaner. Please help!!!

  8. #7

    Join Date
    Apr 2012
    Posts
    548
    Location
    Texas
    Mower
    Troy-Bilt Super Bronco

    Re: Stihl MS460 wont start

    I'm sure you already know this but an engine needs the right amount of air, the right amount of fuel, compression and spark at the right time to operate properly. If one of the above factors are missing or in the wrong proportion the engine will not run or may run poorly.

    Is the spark plug wet with fuel? If not, I'd put a small amount of two stroke mix directly in the cylinder through the spark plug hole and try starting it. Make sure the choke is wide open. If the engine "burps" then you are on to something. Double check that plug and tell us the condition of it - wet or dry?

  9. #8

    Join Date
    Jul 2011
    Posts
    189
    Location
    Mississippi
    Mower
    John Deere

    That's what I have been doing. I have put it in the spark plug hole and the carb venturi. Neither one does anything. Of course after doing that the plug is wet. I also used compressed air and dried the cylinder out to make sure it wasn't too rich in there and tried again. Brand new plug too.

  10. #9

    Join Date
    Apr 2012
    Posts
    548
    Location
    Texas
    Mower
    Troy-Bilt Super Bronco

    Re: Stihl MS460 wont start

    If everything was correct the engine would have at least "burped" to show some sign of life. However since this didn't happen it's leading me to believe the coil is weak. What kind of spark checker did you use? You can easily make your own spark checker from a known good spark plug by clipping the side electrode off at the base where it connects to the rest of the plug. By doing this you will force the coil to produce the maximum amount of energy to jump the much larger gap instead of the usual .025-.030 of a regular spark plug. Try that and see what happens. Make sure the metal body of the tester plug is grounded and the spark should jump to the side of the tester plug. If the coil cannot make the spark jump the larger gap, the coil is suspect.

    Did you ever go the the local Stihl shop and ask the kind folks there if you could borrow a test coil?

    You mentioned that when you put some fuel in the cylinder through the spark plug hole the plug gets wet from fuel-this is what leads me to believe the coil cannot produce sufficient enough spark under compression to start the engine.

  11. #10

    Join Date
    Jul 2011
    Posts
    189
    Location
    Mississippi
    Mower
    John Deere

    I used a regular spark tester from a parts store. I had the gap between .30-.40. It was a food blue spark. I also check the plug by grounding it to the cylinder. Same result. I have not made it by the Stihl shop yet.
    If it was not producing a good spark under compression would it not produce a good spark with the decompression valve pressed. I don't have much experience with the decompression valves.
    This saw was purchased from a pawn shop and has not run since purchased. So I don't know any history on it. It just has me going nuts. Haha!!

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