I have a John Deere STX 38 ride on mower and the engine, which is a 12.5 hp Kohler, has no spark. It has been slowly getting harder to start and running badly. I suspect the coil has died. On other advice I have disconnected the small wire to the coil (earth!) and have tried for spark with just the plug lead, and have nothing. Does this mean the coil is dead, and how can I check the coil to confirm! I have a digital multi meter (albeit a cheapy) but don't really know what I should test or look for. Any advice is appreciated. Cheers.
jmma,
Jan 12, 8:26am
Replace coil. Local mower shop may have a coil tester. Are there any other wires going to coil!
40wav,
Jan 12, 8:33am
Thanks. No other wires, just one small one and the plug lead.
kazbanz,
Jan 12, 8:34am
40 wav--Im NOT saying you are wrongbut apply the KISS principle first. Makie sure all the earth leads are in good condition. that the power is getting to the coil that the plug lead isn't part pulled out etc.
taipan4,
Jan 12, 8:37am
I have one of these with no problems but am picking the ignition system will be electronic (i.e) pointless &either your electronic bit has died or the coil is deadPlease post on your success or otherwise for future ref thanks
jmma,
Jan 12, 8:40am
Come on guys, mowers dont have power going to the coil!
mugenb20b,
Jan 12, 8:41am
Probably a long shot, but check the micro switch under the seat, not sure if your one's got it or not. Also, check any wires that might have chafed through on the frame.
40wav,
Jan 12, 8:44am
Kaz, have checked all that already, but thanks, as it is easy to get too complicated too quickly. taipan4, yes electronic ignition (no points), and the coil is really the electronic bit as there's not much else as far as I can see. I'll take the coil to the mower shop tomorrow and see what they say and will post progress. Cheers all.
40wav,
Jan 12, 8:46am
It does have one but is only active when the electric clutch for the blades is on. Have checked all wiring (not much to check.)
jmma,
Jan 12, 8:47am
I would think by disconnecting the only wire going to the coil, you would bypass all that.
40wav,
Jan 12, 9:12am
How big should the gap be between the coil and the fly wheel magnet!
jmma,
Jan 12, 9:23am
Just use a business card
studio1,
Jan 12, 9:28am
The small wire could be the ground connection (provides the path for the return energy of the coil) or it could be the kill wire in which case it would go to the STOP button. If it's the ground connection, you will get no spark at the plug if you disconnect it. If it is the ground connection you can test the coil for continuity - use your multimeter for this. Set it to ohms (20k) and put one probe on the spark lead contact, the other probe on the small wire. You should get a reading. If you get nothing, the coil is most likely open circuit and needs replacing. It is possible it has shorted turns, and you can't check that with a multimeter. The only option there is replacement. All of this advice is based on the engine having a basic magneto-coil ignition. If it has an electronic module attached to the coil, it's a different story altogether.
40wav,
Jan 13, 6:01am
Hi all, I got a good second hand coil today and fitted it. That fixed it and it's back up and running. Thanks for all the advice given.
jmma,
Sep 13, 6:06pm
Knew you could do it (o:
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