spark plug firing/not firing

Discussion in 'Electrical' started by Samdallas214, Mar 16, 2013.

  1. Samdallas214

    Samdallas214 Member

    I have a happy time that is doing the strangest thing.

    The spark plugs fires if it not in the engine but the second you put it in the engine there no spark .

    I have replaced the coil and plug, checked for shorts wire touching each other . wires touching the frame, any thing to do with wiring you can thank of.

    I have used a tester/inline tester and even checked the tester, that how I know fires when out of the engine but not in the engine .

    What the He!! can be causing it?


  2. BigBlue

    BigBlue Active Member

    What about the spark plug wire? Have you replaced the crappy one with the kit with a quality wire? Have you checked the spark wire for breaks or cracks? Try removing the kill switch and see what happens. It might be grounding out. I assume that you've replaced the spark plug with a quality plug. Check to make sure the plug wire is securely connect to the CDI. If that doesn't do it, follow this no-start guide from forum member AI.Fisherman. You are going to need a DDM to check the Ohms. You can buy one at Harbor Freight for $4.99 or sometimes they are giving away free:

    Here's another good guide from Grubee on troubleshooting: cycle engine trouble shooting guide.html

    Good Luck,

    AKA: BigBlue
  3. V 35

    V 35 Member

    Sounds like a cracked plug, snow mobile guys tell me this happens in the cold, a lot . The plug fires OK when * not * under
    compression, compression opens the crack = no spark. They told me, test a , new spark plug in a lawn mower engine, if it starts, mark the plug as ' good ', pad it carefully, and store it where you can find it, a tested good plug, beats a new / untested one every time.
  4. jaguar

    jaguar Well-Known Member

    Within the engine there is compression that makes it harder for the spark to jump the gap.
    The standard CDI is designed to just barely do the job so any little change in it makes it useless. That is one reason I invented the Jaguar CDI. Check out the info about it on my site and see the video that shows a spark gapping 5 times the normal gap. Time for an upgrade!
  5. Fabian

    Fabian Well-Known Member

    what we need is for you to make a proper high power coil.
  6. Samdallas214

    Samdallas214 Member

    well I got it to start and get fire .
    Somehow a small piece of metal got down into the spark plug hole , it was stuck and so black it could not bee seen until I disassembled the engine and found a small piece of metal.
    Strange but I thank the metal was grounding the spark plunge keeping it from firing.

    Tom now has it back and was told to keep the kids away from it.