John Deere 38 STX starting problem?

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Old 05-06-12, 06:02 AM
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John Deere 38 STX starting problem?

I have a '95 John Deere 38 STX lawn tractor. Just went through it 2 weeks ago. Cleaned the mower deck, sharpened the blades, changed the oil, cleaned the spark plug and replaced the air filter. After that, I just "touched the key" and it fired right up! Next time out, it started a little hard. Yesterday, the motor would crank, but it never fired. I found that the plug wire was loose, but upon re-attachment, it still would not start. I called the local John Deere dealer and they said that the Kolher 12.5 engines are famous for having starting problems and that it "may" be the ignition module ($ 62.), but he wasn't sure. For them to inspect it would be another $85. more, and they could not look at it for 2 weeks! How can I tell and where is the "ignition module"? FYI - I bought a new spark plug (as I can't remember ever replacing it), but have not installed it yet.
 
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Old 05-06-12, 06:06 AM
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Just wanted to add that in the 17 years that I've owned this lawn tractor, it never had the "famous starting problem" that the dealer was referring to?
 
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Old 05-06-12, 11:00 AM
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For the starting problem to be so famous, funny I don't know about it either even after twenty some years of working on them.

Check for spark when cranking (good time to put that new plug in too). If you have spark, check the choke operation. I do find that kohlers are a bit more finicky about having the choke on 100% for them to start. Sometimes the choke will close, but not all the way.
 
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Old 05-06-12, 11:54 AM
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I finally got back out to work on the tractor this afternoon.I pulled the spark plug wire, put the new plug on it, left it hanging and turned the motor over - - - NO SPARK! so, should I replace that ignition module that the John Deere dealer talked about? Also, where is it located and can I get it cheaper online?
 
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Old 05-06-12, 01:50 PM
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If it was just hanging, it won't spark. The plug needs to be in contact with a metal part of the engine for it to spark. Post back with results. If no spark, the module could be bad, but there is more testing to be done before coming to that conclusion.
 
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Old 05-06-12, 03:01 PM
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OK - call me electrically stupid! I took the spark plug out and, with the wire connected, touched the threads on the plug to a metal tab on the engine, then turned it over - still no spark. What to do next?
By the way - thanking you, in advance, for all your help!
 
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Old 05-06-12, 03:20 PM
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Take the engine shroud off and you will see the ignition module. Unplug the white wire that is plugged onto the bottom of it and re-check for spark. If still no spark, the coil/module is bad. If you do have spark, there is a problem in the wiring or safety switches.
 
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Old 05-06-12, 05:27 PM
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OK - I will check it out, but it is getting dark & it's raining now. It's supposed to rain here all day tomorrow and the tractor is in the "shed" out behind the house. I will make every attempt to get at it tomorrow (Monday). As soon as I do, I will get back with you to update progress.

Again - Thank you much.
 
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Old 05-07-12, 11:27 AM
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HEY - SUCCESS!!! Here it is 2:25 PM and the job is done. My little John Deere STX 38 lawn tractor now starts when you just "touch the key"! Turns out that it was the ignition module. FYI - set the air gap at .012".
Thanks a bunch. What a great website! - - - Dan.
 
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Old 05-07-12, 06:49 PM
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Great! Glad you got it! The deere guy's hunch was right after all. Coil problems on Kohlers aren't really that common though. I do maybe 2 or 3 per year out of however many hundreds or maybe thousands of engines that I work on (not all kohlers).
 
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