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Discussion Starter · #1 ·
I was mowing this past weekend and the mower (STX38 w/yellow deck) just shut off like the seat safety switch had opened. When I tried to restart, the engine turned over strong but would not fire. I'm half way dangerous working in my mowers (this STX38 at the lake and LX176 at home). Since it was 95 degrees, I just pushed it back under the shed and decided to repair it later. The mower is at the lake an hour away, so I'm trying to line up what I might need to take with me when I go up next week to troubleshoot and/or repair the mower. I did not check to see if it was getting fire at the plug or anything like that. But it does have fuel and fuel to the clear fuel filter.
1. Other than the seat interlock switch, does anyone know where another interlock switch may be located...or if there is another one.
2. I've had friends who had to replace what the JD parts manual calls the regulator that is mounted on the side of the engine schroud...anyone think that may be the issue?
I'm just looking for some "try this or that" from my fellow forum friends. Thanks in advance! :dunno:
 

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Since the engine turns over but does not fire, I doubt it is a safety interlock. Most of the time the safetys will also keep them from cranking. But for reference along with the seat switch there should be a brake switch, neutral switch.

Make sure to take a volt/ohm meter along for measuring voltages and resistance.

First need to see if it lacks spark or fuel. Could try some carb cleaner or a little fuel in the carb and see if it will fire for a few seconds. If it does, you might have the fuel shutoff solenoid option on the bottom of the carb on that. Would be the first thing to check if you do. Make sure your getting voltage to it so it opens and allows fuel to pass.

If no spark or it runs until it gets hot again and then no spark I would look at the ignition coil making sure the lead from it that goes to the key switch is only grounded in the off position I think the regulator if it fails will only cause a lack of battery recharge.
 

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Actually Mark on STX and Kohler Command engines ,they can crank and not fire . I have a few that gave me fits until I use spark tester and actually saw that seat switch was active! I installed a Command on our Yard-King and it is wired so if you get out of seat for ANY reason, even with brake on the spark is stopped!
 

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That' irritating! Going off what Eric said, you should definitely check the seat interlock. Just put something in the seat to represent you and do a spark check. Then you can go from there.
 

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You make a good point Eric. When I get on my laptop again I'll pull the electrical diagram back up and see if I can post some snips from it. Thinking back I believe the seat switch is a double throw. So the side that kills the crank could be ok yet the side controlling the spark could be bad. On mine I believe only the cranking is killed by the brake switch but they kill both the crank and spark with the seat, pto (manual) and RIO. I don't think the STX series had the RIO? They have electric pto by the diagram. But that does still leave the seat switch as a possible to kill spark.

Whether or not the kill wire to the coil is grounded which also looks to tie to the M terminal on the key switch would give a good clue if need to trace back through the interlocks.
 

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Hey Mark, it drove me nuts once! Could not get this one to start!! Then happen to sit on it and try one more time...... fired right up! Got off and died! I have to figure out why the Yard-King is wired this way to stop it from killing engine with brake on! Hard to let it run out of fuel or cool off when unloading bagger! :(
 

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Turns out the seat is a single throw switch but they are using a start relay to tie together the cranking and spark kill circuits. There are four diagrams depending on serial number. Guess that is one reason the tech manual is 314 pages. :dunno: I attached the four diagrams (8 images). A1 & A2 are the same serial number run. B1 & B2 are the same serial number run etc. Serial numbers for the images are at the top of the page. Also note there are page numbers at the bottom of the images to tie them together.
 

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SWEET Mark! Explains the issues with one I have behind house too!
 

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Discussion Starter · #9 ·
You guys rock! Thanks so much. I also chased down some wiring diagrams last night, but it's great that you pasted several here. As for fuel, I don't think it's fuel because it shut off so quickly. I stopped running just like I had stood up and the seat switch was actuated to shut off the engine. This is all good info and thanks for bouncing the ideas. I'll let you all know what I find out.
 
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