Kohler 17.5 won't start, cranks hard, and backfires

Discussion in 'Mechanic and Repair' started by davidcalhoun, May 14, 2006.

  1. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Posts: 1,022

    Need some quick trouble shooting help. My neighbor has a 2004 John Deere LT118 that will not start. While he tried to start it after sitting in his shed for a week, it backfired loudly. After that, he ran the battery down while trying to start it. Note - it is stored in a outdoor shed and we have had 5 straight days of rain.

    This is where I came into the picture.

    I checked his battery to make sure he did not have a dead cell. It was OK. I then put a battery charger on it.

    I tried to start it and it cranked very hard and backfired hard with the choke on. With the choke off it cranked but never fired. He said that he has always had to start it with the choke fully engaged.

    I also pulled out the spark plug and checked it for spark while grounding it. It seemed strong and fine.

    The spark plug also seemed to be getting fuel.

    Any suggestions from this point on would be appreciated.

    Dave
     
  2. LawnInOrder

    LawnInOrder LawnSite Senior Member
    Posts: 398

    davidcalhoun, when you say you were cranking it, was it cranking fast or slow. If it is cranking too slow the engine will not start. if you say you are getting fuel and it is cranking hard, check the compression.Is it a 2 cylinder engine or 1? if it has compression check the ignition timimg to see if it is off or the spark plug gap. When was the last time the machine was used? just my .02 LawnInOrder
     
  3. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Posts: 1,022

    The mower was operating 6 days ago with no problems.

    I had the battery fully charged before attemping to start. It was cranking at normal speed.

    Spark plug was new and properly gapped. Lots of spark.

    So is the timing the next thing to verify/correct or is there something else that I should check first? Thanks.
     
  4. MowerMedic77

    MowerMedic77 LawnSite Bronze Member
    Posts: 1,164

    Is the backfire coming out of the exhaust or from the carb?
     
  5. LawnInOrder

    LawnInOrder LawnSite Senior Member
    Posts: 398

    ok, check the fuel maybe the water from the rain might have gotten into the tank. Check the compression even though it sounds as if you have a rpoblem with the carb. Also mowermed ask Is the backfire coming out of the exhaust or from the carb? LawnInOrder
     
  6. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Posts: 1,022

    I thought that the backfire was coming out the muffler. Now that I have had the air filter off while cranking it, I am not sure. I will pay more attention to it tomorrow when I go over to my friends house after I done with work.

    One thing that I noticed is that right after a backfire, the engine is hard to crank for a second. After that it cranks again until it backfires again.
     
  7. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    It may be the flywheel key. That can cause your problem. Just another thing to check.
     
  8. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Posts: 1,022

    Thanks for the help so far. I am sure that I'll need more direction.

    Had some time already tonight to dive into it some.

    I just tested the fuel system. Fuel pump works and the fuel shut-off solenoid is operating (opened and closed when I added 12 volts).

    While I had the air filter off, I tried to start it again. It still did not start but the backfire is definitely coming from the muffler.

    Looked over the carb while I had access to it and blew it out with air and then sprayed carb cleaner in it.

    I'll pull the cover off flywheel area next to see if the flywheel key is sheared.

    Dave
     
  9. davidcalhoun

    davidcalhoun LawnSite Bronze Member
    Posts: 1,022

    SUCCESS. It's running. Thanks everyone.

    It was a sheared woodruff key on the flywheel. The key was a 3/16" X 5/8" and I had a hard time finding that size. Even John Deere did not have it in stock.

    I asked my neighbor if he had hit or run over anything that may have caused a stress to the engine enough to make it shear. He said no. I still wonder why it sheared.

    Now I get to make a fake bill for him that will involve his wife and baby oil.

    Dave
     
  10. khouse

    khouse LawnSite Bronze Member
    Posts: 1,465

    Dave - we will need pictures of the wife with the oil on her for all our troubles.
     

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