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I have been pulling my hair out over this 'overheating' (?) John Deere. It has a Kawasaki 600V-as21 engine and will shut down usually after 15-30 min. mowing. My first thought was coils. I bought new Kawi coils. same result. I removed anti-backfire solenoid. same result. I replaced spark plugs with new and colder, pulled sheet metal and blew out around engine, adjusted valves, installed larger fuel filter, cleaned carb., and even sharpened the blades. Is it possible a safety switch could be cutting the spark out after heating up ? I just ran out of options ...

3 things make an engine run

air/fuel ratio
compression
spark

Figure out which one is missing when it dies and then chase that path. Shotgun approach works sometimes but at this point figure out what is missing. You can get a plug tester or timing light to see if the plug fires when it dies. If spark is missing it can be anything in the ignition or ignition supply side. If you have spark then do a quick compression test. Next is maybe something in the fuel supply, tank venting etc..

sgkent said:

3 things make an engine run

air/fuel ratio
compression
spark

Figure out which one is missing when it dies and then chase that path. Shotgun approach works sometimes but at this point figure out what is missing. You can get a plug tester or timing light to see if the plug fires when it dies. If spark is missing it can be anything in the ignition or ignition supply side. If you have spark then do a quick compression test. Next is maybe something in the fuel supply, tank venting etc..

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Thanks for your reply. I have a spark tester and had it on the mower with me. It's definitely losing spark. When it cools down, maybe 5-10 min., it will fire up and run again for maybe 5 minites and shut down again. Fuel pump is working the entire time. Not a fuel problem. It quits like you turned the key off.

Not familiar with x300 wiring offhand but does your mower have a time delay module? It is part of the JD wiring and not the Kaw engine.

Next step is to remove the kill wires from the coils and see if the problem persists
This will show if it is an engine problem or mower wiring problem
Let us know what happens

Hammermechanicman said:

Not familiar with x300 wiring offhand but does your mower have a time delay module? It is part of the JD wiring and not the Kaw engine.

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I wasn't familiar with this model until this week. It belongs to an elderly neighbor and it does have a delay after you switch the key to OFF.

bertsmobile1 said:

Next step is to remove the kill wires from the coils and see if the problem persists
This will show if it is an engine problem or mower wiring problem
Let us know what happens

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I will try that today and let you know. Thanks.

The time delay modules die all the time. If you have a piece that looks like this try changing it and see what happens

Thanks for the tip on disconnecting kill wire. I mowed for about 30 min. when it quit the first time and fired back up when I placed spark detector in line. I left it on and went mowing, it died 5 min. later. It would not start back up. I verified no spark again and disconnected kill wire. It fired up immediately and mowed for another 30 min. without a problem. Is the ECM the problem ? What else would act like that ?

Thanks for the tip on disconnecting kill wire. I mowed for about 30 min. when it quit the first time and fired back up when I placed spark detector in line. I left it on and went mowing, it died 5 min. later. It would not start back up. I verified no spark again and disconnected kill wire. It fired up immediately and mowed for another 30 min. without a problem. Is the ECM the problem ? What else would act like that ?

Hammermechanicman said:

The time delay modules die all the time. If you have a piece that looks like this try changing it and see what happens

https://www.amazon.com/Electrical-Delay-Module-Replaces-AM128906/dp/B07SG29KH7

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Thanks for info, I didn't find anything that looked like that under the dashboard.

Won't be under the dash. If the mower has time delay when you turn the key off it either has time delay module on the side of the engine or has a circuit board connected to the ignition switch.

Hammermechanicman said:

Won't be under the dash. If the mower has time delay when you turn the key off it either has time delay module on the side of the engine or has a circuit board connected to the ignition switch.

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I looked all over the mower and didn't find anything that looked like a time delay. Would the ECM act like the time delay when you turn the key off ?

Ok get your mowing done , carefully, for now then it will be time to track down the actual problem
At this point in time I very strongly recommend you buy the JD technical manual for your mower.
The electrical section starts by telling what each bit does & how it works , then follows up with exactly how to test the mower with nothing more complicated than a multimeter and finishes by showing exactly where on the mower each switch is hidden .
It is not cheap , but good is seldom cheap and will pay for itself in bottles of burbon not needed to calm your frayed nerves and repairs to the holes in the wall you threw your tools through in frustration .
JD seem to believe in the old engineering adage
" there is nothing so simple that works so well that it can not be made better by making it more complicated "
Even worse is JD will have multiple different wiring on the same model plus different wiring again for the USA, South America , Pacific, Europe etc .
If I had a diagram for am X300 I would have posted it but I don't .

bertsmobile1 said:

Ok get your mowing done , carefully, for now then it will be time to track down the actual problem
At this point in time I very strongly recommend you buy the JD technical manual for your mower.
The electrical section starts by telling what each bit does & how it works , then follows up with exactly how to test the mower with nothing more complicated than a multimeter and finishes by showing exactly where on the mower each switch is hidden .
It is not cheap , but good is seldom cheap and will pay for itself in bottles of burbon not needed to calm your frayed nerves and repairs to the holes in the wall you threw your tools through in frustration .
JD seem to believe in the old engineering adage
" there is nothing so simple that works so well that it can not be made better by making it more complicated "
Even worse is JD will have multiple different wiring on the same model plus different wiring again for the USA, South America , Pacific, Europe etc .
If I had a diagram for am X300 I would have posted it but I don't .

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Thanks for your input. I found a wiring diagram and studying it, I'm leaning toward the ECM being my culprit.

The ECM module ( if you can find where they hide them ) is an expensive part to replace when a $ 5 relay could be the culprit .

bertsmobile1 said:

The ECM module ( if you can find where they hide them ) is an expensive part to replace when a $ 5 relay could be the culprit .

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I haven't found any $5 parts on a JD mower

if disconnecting the coil kill wire(s) stops the problem, if the repair cost is too high, could one add a kill switch toggle, label it and use that when shutting down the engine? In my mind's eye, anything that might trigger a shutdown in the logic could be the failed component. For example, let's assume for now that the ECM sends a kill signal when it is told to shut the engine down. If the ECM goes bad it could do that as a failure - but if say a safety switch is going bad, it could be sending an unwanted signal to the ECM to shut down. I think the advise to buy the manual is the path I would take. It is possible that more than one safety switch is involved, or even a connector that is corroded. Meaning - let's say the ECM expects 12V on a certain pin when it is safe to run, if there is a corroded connector that causes that pin's signal to go away then that could cause it. Unless one has the manual to detail the logic the system uses, I think it would be quite time consuming to dissect how the system is supposed to work electronically.

I have the same issue on a 2012 x300 so am very interested in the result. I have done the obvious and confirmed the cap vent works, replace the seat switch, and fuel pump. I have confirmed the issue is related to spark so the ECM is next but would prefer to be able to confirm before buying a $100 part.

Campers99 said:

I have the same issue on a 2012 x300 so am very interested in the result. I have done the obvious and confirmed the cap vent works, replace the seat switch, and fuel pump. I have confirmed the issue is related to spark so the ECM is next but would prefer to be able to confirm before buying a $100 part.

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The owner said go ahead and buy the ECM, she's paying, so I did. Installed the new ECM, started the mower fine but, key switch would not kill engine. ?? I cleaned all the safety switch connectors and PTO switch connector. I has worked without issues since. I can't say now if it was the ECM, dirty connectors, or both. Good luck !