Kohler Command Pro 20 HP won't start or won't stay running.

3411 Views 7 Replies 5 Participants Last post by RedOctobyr, Nov 8, 2020

wiz222

Discussion Starter · May 28, 2019 (Edited)

I recently purchased a 20-year-old stump grinder with a Kohler Command Pro 20 engine. It didn't run and according to the seller, it ran last fall but wouldn't start when he tried it this spring.
It appears to have been modified to add a pushbutton start button.
So far I haven't been able to keep running when it does start. Mostly it doesn't even seem to fire. It does not crank when you twist the key but does when you push the button.

Symptoms
It usually doesn't start, but sometimes it does start and dies almost immediately. When this happens it won't usually won't start again.
When the key is turned to "on" I hear a click which I assume is the carb solenoid. To test the solenoid, I ran a jumper wire from the battery to the solenoid and tried to start it. It did not start.
I bought an ignition tester and see it light up when it does run. It's very dim when it cranks. I had to try it after dark to see it light when cranking. It may just be a junky ignition tester light.
I next rebuilt the carb with a carb kit. While off I verified that the solenoid activates when 12V is applied.
Looking for suggestions for the next steps in diagnosing and fixing it.
TIA,
Paul

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dave_r

· #2 · May 28, 2019

check that the choke & throttle plates move appropriately
try starting the engine for a bit, then look at the spark plug (is it wet or dry, does it look like the engine was running lean or rich or burning oil)

Actually, I would suggest finding and downloading the service manual for your engine, and going through the diagnostic procedure in it. The download should be free (it was for my Kohler CV22S).

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38racing

· #3 · May 28, 2019

See if it wants to start with a bit of carb cleaner into air intake. If it starts and runs a bit then try again but continue spraying and see if it continues running. You say you put a carb kit in it but did you clean the carb?

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RedOctobyr

· #4 · May 31, 2019

Check spark by resting the plug against the engine block, with the wire connected, and watch for a bright blue spark when cranking.

You could also try the ignition tester on another engine, to see if it's brighter.

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wiz222

Discussion Starter · #5 · May 31, 2019

38racing said:
See if it wants to start with a bit of carb cleaner into air intake. If it starts and runs a bit then try again but continue spraying and see if it continues running. You say you put a carb kit in it but did you clean the carb?

Yes, I cleaned the carb when I rebuilt it. I had tried starter fluid (but now know that's bad for small engines) I'll try carb cleaner this weekend.

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tomw0

· #6 · Jun 2, 2019

Starting ether is not something to use regularly, but judicious use should not cause permanent damage.
An alternative to that and carb cleaner(some will not do what you want) is gasoline. You can dribble a teaspoon of fuel into the inlet(remove the air cleaner or top, and dribble it in), and then trying the starter. The fuel will vaporize, and get drawn in just as if it came from the float bowl, and if the engine lacks for fuel, it should start and run for a few seconds.
If you have not done so, remove the spark plug, inspect for deposits, clean as needed, adjust the gap, and then check that the magneto works. Re-attach the high tension lead from the coil, place the plug so the shell touches the engine, and crank. You should be able to crank faster(no compression), and should see a good fat spark across the gap. If not, disconnect the kill wire leading from the engine to the controls, and re-try cranking. Sometimes the wire gets damaged, and grounds the magneto as if you had turned the key to OFF. Sometimes the switches get damaged, ditto.
tom

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wiz222

Discussion Starter · #7 · Nov 7, 2020

Just realized I never did a follow up on this thread I started. I gave up fixing it and took it to my local small engine guy. He rebuilt the carb again and it still wouldn't start. He called the factory and they said to check the coils. He replaced both and it resolved the issue. I hadn't thought that both could go at the same time. I had tested both with a coil tester and both looked the same but weak. Since I had never used the coil testers before I didn't pick up on the fact both were going bad.

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RedOctobyr

· #8 · Nov 8, 2020

Cool, thanks for posting the resolution!

You can sometimes also help check for a weak (but "functioning") spark by reducing the spark plug gap, and see if the spark improves. The smaller gap helps allow a spark even with a weaker coil. That's not an ideal long-term fix, but it's an easy test, and it can help you get by for the short-term.

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