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John Deere 140 No spark

8502 Views 34 Replies 8 Participants Last post by  lisle
Ive got an early i believe John Deere 140. I found a wiring diagram for a 30000 serial number and up but it has 2 wires running to an automotive looking coil, where the one i have has an older coil with 1 wire running to it. I would go get the serial number but its late and its out in the shop...

Ive got no power to the coil when i turn the key on, but when i crank the engine i do get power pulsing to that wire. Would that suggest a bad coil? or should the coil have more constant power.
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016785m is the tractor serial number. Can't see one on the block. Not sure what type of ignition it has. Haven't dug too deep. Here is a pic of the coil. Sorry, forum made me make the pic aweful small.

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Yeah the wire broke off. I fixed it after the photo. I just went out there half our ago. Had spark ran great. Let it sit. Just now tried to start. No spark nothing. Rattled the wires checked plugs nothing. So this ignition setup is known to cause problems?
Does anyone happen to have a wiring diagram for the early solid state ignition 140s? I almost want to say it is the kill switch that could possibly be bad. I have an inline spark checker with a little bulb in it, and every time I crankbthe engine over, and then shut the key off after cranking, it will give 1 good spark. This normal?

If I were to switch to the other ignition type, what all does that involve wiring wise? Thank you for your help!
What wire is the kill wire? And I assume it is grounded to kill? Or is it a hot ignition wire? I was going to bypass the key switch to see if I've got spark. If I do I know thy is my problem. Not looking to disable any safety devices, just troubleshooting
So I have the ignition switch out. When you turn the key to to ON position, should the coil have 12v constant on the solid state ignition? When cranking or key on, I have no spark or constant 12v at the coil. If I put my testlight on the coil wire it will pulse while cranking. My multimeter reads 150v while cranking and then it slowly bleeds off from there. But that cant be correct or elae kt would blow up the test light. Everything I see leads me to a bad coil or ignition switch. Just CNT figure out if I'm supposed to have 12v constant or not. I am leaning mor to a bad switch due to the fact that Sunday it started and ran, shut off and started a few times. After sitting a bit it did not run.
I wish I could find a wiring diagram for this year. Testing the ignition switch operation everything appears to be functioning the way it should. Now when cranking and shut key off I get one spark. So I grabbed a test lead and hooked it to the coil wire. While cranking every time I grounded the wire I got a spark. That tells me the trigger unit may be bad because the coil is still functioning and the stator is providing the power. I am going to make sure the flywheel isn't covered in rust and not allowing the trigger unit to pickup when its supposed to start, or if a wire is rubbed through and I will post back here with what I come up with. Thanks for the help everyone.
To be honest, it is not my machine but a neighbor here is town. It has seen quite a few hours of work by the looks of it. Found the wires to the trigger unit had the coating chewed off of then. Repairing them and going to see were that gets me. Thanks again for the diagram. All I have been able to find is the 30,000 and up diagram
I'm just highly confused. Cleaned off the pickup on the flywheel, ran a new lead from trigger unit to coil, and tractor fired right up. Shut it off, let sit a minute, fired right back up. Let itnsit 10 minutes and now no spark again. It is not the ignition switch as I have the coil wired directly to the trigger unit for testing. I am still getting pulsed power to the coil.. Everything checks out including the coil resistance tests.
Roger I appreciate you guys putting up with my stubbornness in thinking I can make this work. I'm to the point where I think its worth the roughly $175 for the kholer breaker point conversion as was mentioned early on in this thread
Got the go ahead to put points on the old girl. Shouldn't have any more problems after this install.
Now, to install points, is this where they mount? I'm notnseeing the plug that needs knocked out. In wish I could tell you the exact engine this is. There is no plate or serial number I can see

Edit: Or is it that small hole about an inch above the flathead screw? I was looking for a much larger hole
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Thanks guys. From what I read the stator doesn't need changed. Its job now is just to charge the battery, and the ignition will now run on the battery. Am I wrong?

And I got all the parts for right around $85. Coil points pushrod, coil bracket plugnwire and ignition switch.
Well I ended up doing the points conversion. Used the same stator and it still charges the battery and ran good. So I say it was a success!

Thanks everyone again or your help!
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