Plug not firing

paul03August 23, 2010

I have a kawasaki engine FH721V and the left plug does not fire. I replaced the ignition coil for that side along with new plugs and it still does not fire the left plug, the right plug works fine. This engine has 350 hours of work and it is 7 years old, this problem just startd. What else should I be looking for to get this plug to fire.

Thank you

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Can you see that the plug isn't firing? I had a similar problem with my Onan engine, but I think it was more of a fuel or valve related problem. It only did it on a cold start, where it would run on one cylinder until the second one kicked in.

    Bookmark   August 23, 2010 at 7:51PM
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As said above, are you sure there is no fire? Don't know about Kawas. but B&S and Kohler have a weird "kill wire" ass'y connecting the two coils. When a one of the diodes in this goes out, all sorts of weird things happen. I would disconnect the kill wire at the base of both coils and see what happens.

Walt Conner

    Bookmark   August 23, 2010 at 10:31PM
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The problem with the plug not firing started with black carbon on the engine and inside hood. I then put in new plugs gaped .030 and cut the grass for 1 hour. I removed the plugs to check their condition and found the right plug had the gray/black tint that it was firing, but the left plug was in the same new unused condition, not a spec of anything on it. As for the wiring, a wire comes from the main harnes to the right ignition coil, from that connector a second wire goes to the left coil, with nothing inbetween.

    Bookmark   August 24, 2010 at 2:29AM
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If you mowed for an hour on one cylinder and the non-working cylinder still has an original looking plug, I would check the compression first, and look for something broken. Your plug should be gas soaked, or gas should be running out of the muffler.

    Bookmark   August 24, 2010 at 6:05AM
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