John Deere 112 ignition troubles

300 dave

Member

I am at wits end. My 112 JD circa 1970 will not spark enough to fire. I check the spark by inserting a screw driver in the plug wire holding near steel as I turn engine over. This shows a blue spark about 1/32 long. Should be 1/4 anyway. I have installed new-coil-points and condenser. I have tried several plug wires. Same thing. Anybody know what the problem is here?
 
It would be helpful to know the serial number as (IIRC) both Kohler and Tecumseh engines were used at various times, and some had magneto ignition and some had Kettering ignition.

If magneto ignition it's important that there's no leakage to ground in the kill circuit and if Kettering ignition it's important that full battery voltage is getting to the coil when cranking or running.
 
I will check tomorrow in daylight, it is a Kohler. I have suspected a need for new wires to coil as old is hard and kinky. Is there any way to test that wire for leakage? maybe a multimeter?
 
(quoted from post at 19:09:12 08/22/21) I will check tomorrow in daylight, it is a Kohler. I have suspected a need for new wires to coil as old is hard and kinky. Is there any way to test that wire for leakage? maybe a multimeter?

So dies it have "round can" external coil (Kettering ignition), or is the coil under the flywheel (magneto ignition)?

If an external coil/battery/Kettering ignition, what I said about checking for leakage to ground in the "kill" circuit would not apply.

Of course, primary wires need to be in decent condition either way.

If "battery ignition", are the coil and condenser connected up properly, power from ignition switch to (+) terminal post on coil, condenser and breaker points to (-) terminal post on coil?


http://resources.kohler.com/power/kohler/enginesUS/pdf/tp_2379.pdf

The link above is to the official Kohler Service Manual for that engine (in .pdf format), you can view, download, or print it as you desire, for FREE.
 
Kettering ignition? had to google it.

More commonly known as 'Battery ignition'.

Now to actually fix it:

Your battery is good, isn't it?

Does the wire to the points go on the (-) post on the coil? it should.
the (+) side of the coil should have the wire from the ignition switch.
You do have a correct 12v. coil, don't you?

Does your condenser go to the (-) side of the coil? it should. It can also mount down at the points, but mounting it down there can be tricky.

Your condenser won't work unless it is grounded. So mount it securely.

Gap your points to about .020. Use a genuine feeler gauge. They're cheap. ( I know about timing them but this will be close enough to start it.)
Clean your points with a piece of clean paper slid back and forth between them.

Your spark plug wire. Is it a steel or copper wire or is it a resistor wire? It should be a steel one. Some resistor wires work and some won't, too much resistance.

If you have done all this, try substituting another wire from the points to the (-) of the coil.

Another thing that occurrs to me: My 112 had the engine mounted in rubber dampers. See if it helps to add a ground wire from the battery (-) to the engine.
 
Run a temporary wire from your battery + side to the + side of the coil. This will eliminate a lot of wire connections along the way, and may tell you something.

As mentioned earlier, all coils are not created equal. You MUST have the CORRECT coil.
 

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