Kohler CH25S not runnin on one cylinder

Discussion in 'Mechanic and Repair' started by treeguy27, Feb 25, 2008.

  1. treeguy27

    treeguy27 LawnSite Member
    Posts: 15

    Newbie here looking for some help with this Kohler. It's a Kohler Ch25S spec# 68587.

    It is only running on the front cylinder sporadically (starter side). The compression seems fine, fuel seems fine. I've already replaced the coil for this side. I am thinking it may be the Smart Spark module, but not for sure. None of the local shops have the Kohler tester for the Smart Spark. They claim it costs a fortune.

    I looked on Kohler's website but could not find a service manual for this exact engine. I found one for a very similar engine though. I tried to test the Spark Advance module with the a timing light as the manual said. If I am doing it correctly (I think I am), both cylinders are firing at the same time. At least getting spark at the same time. I made a mark on the flywheel screen, then started the engine, found the mark using the timing light, made another mark on the shroud next to the first mark. Accelerated the engine, and the first mark moved slightly away from the second. Then I Moved the timing light to the other plug wire and looked for the first mark with the light. It was still lining up with the mark from the other cylinder. It moved away when accelerated as well, but was not 45% from the first mark as the manual said it should be. It appears both plugs are firing at the same time?

    One other oddity, while running the engine with the shroud off, I had tucked the Spark Advance module under the front plug wire to keep it from getting tangled in the flywheel. When it was placed in close proximity of the plug wire the the cylinder would start running, pull it away and it would stop. None of the wires are cracked or exposed, but if I hold it right next to the plug wire, that cylinder would start running. Is it just interference, or a sign the module is bad. I hate to throw a new module on there if it may not be the problem. The thing ain't cheap, and I've already replaced a good coil.

    Any one have any thoughts or ideas. I am about to pull my hair out with this thing. Have been fighting it for several days now. Any help would be greatly appreciated. sorry for the long first post. Dave
  2. sawman65

    sawman65 LawnSite Senior Member
    Posts: 751

    first pull all connections clean and try again sounds like when you move the sam a connection starts to work again. there is an OHM test in that manual for the coils if the test is good for both coils you would be safe to assume the sam is bad.
  3. Landrus2

    Landrus2 LawnSite Platinum Member
    Posts: 4,812

    Before you go out ant buy more parts. you need to check all your grounds connections, along the line some thing is getting grounded, that is why you lose spark have you looked to see if your spark insulator is not shot.:waving:
  4. kayeproperties

    kayeproperties LawnSite Member
    Posts: 141

    I had the same problem on the same motor and thought it was the module or a weak coil but it did turn out to be a weak connection going to a coil. I cleaned all connections up and made sure all were good wire and tight and sealed and has worked great ever since. I was on my way to get a new module and a new coil just so i could try both but i got lucky and was just moving the wires around and it strated to work better so in a nutshell I think you are in the same boat. Mine would have a backfire or miss at full throttle and it was driving me crazy!!
    good luck
  5. liftstation

    liftstation LawnSite Member
    Posts: 1

    it is an exmark with a kohler sp27 hp. model c74v00036ba serial 3630601141, it runs great for 30-45 minutes then it just dies out,once it cools down about 1-1.5 hrs it will go again. at first I thought coil, is there a way to test the module spark adv. as kohler calls it. thanks for any help anyone can offer.
  6. piston slapper

    piston slapper LawnSite Platinum Member
    Posts: 4,245

    You hijacked a 3year old post

    Search the archives.....then , if you dont find your answers..Start a new thread


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