John Deere 318 dies

Farmtoys · Sep 30, 2015

Hey guys, need help. Onan in my JD318. Runs great for a few times during the week, then once in a while it will die like you killed the ignition. Changed fuel filter, ran some Sea foam through it in the gas (love that stuff). Wait anywhere from five minutes to an hour and it will start and run fine. Can't recall hearing the "click" of the 25A breaker, and as I recall the battery light is still on when it dies. oil is full and clean, gas cap loose or tight makes no difference. JD dealer wasn't any help, only wanted to take it and keep it for a month before saying they can't figure it out....
I can check safety switches (brake and seat) but not sure how.
Thanks!

T.R.K. · Sep 30, 2015

You don't say which Onan you have. You need to find out if you are losing spark when it dies.
If you still have spark, your problem is valves/compression or fuel.
If you lose spark, then something is failing in the ignition.
To test for spark at the plugs, you really need a test plug, I am sure there are instructions on the 'net how to make one.

If no spark, on the P218G, there are 2 tests that I would perform.
Test 1. with the ignition switch on,Take a test light, put it on the smaller post on the oil. It should light. If does not, you are losing power from the chassis of the mower.
If it does light, perform test 2.
Test 2. put the test light on the larger post on the coil. Turn the ignition switch to Start and crank the engine over. The test light should blink if the trigger is working. (Every time the magnet on the crank passes the trigger it breaks the circuit.)
If it does blink, your problem is probably the coil (But check the spark plug wires first.)
If it does not blink, your problem is probably the trigger (or the magnet that works the trigger) behind the flywheel.

Hope this helps.
T.R.K.

Farmtoys · Sep 30, 2015

Thanks a bunch. I will try this and send an update later.

tractorguy2 · Sep 30, 2015

I had a MTD mower once that would just all at once die. Sometimes it would start right up. Sometimes it wouldn't.

It had a bad spot in the wiring harness. The front wheels had to be turned a certain way for it to ground out the coil.

DGinVT · Oct 1, 2015

We had this happen on a portable welder with an ONAN Engine. After some testing it turned out that the coil had failed.

Married2Allis · Oct 2, 2015

(quoted from post at 19:27:44 09/30/15)
If no spark, on the P218G, there are 2 tests that I would perform.
T.R.K.

It sounds like it is electrical because if it's running out of fuel the motor will sputter before it shuts down. But like Farmtoys said it 'Runs', so before testing the ignition I would look elsewhere. First bypass all the safety switches to rule them out. The seat switch is the one gets the most use, so you might start there if it has one. A tractor that old could certainly have shorts in the wiring. After eliminating those, I would completely go through the engine ignition wiring and look for dirty connections and broken wiring to make sure something is not grounding out. Then make sure everything is clean and tight. If still not running right then would definitely test the ignition ... coil, magneto, whatever it has.

John Deere 318 dies

Farmtoys

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T.R.K.

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Farmtoys

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tractorguy2

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DGinVT

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Married2Allis

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