I have a 27 hp kohler on a mud buddy frame. It is intermittently not getting spark when key is in the on position but it always has spark when key is in cranking position. When it acts up it only has spark while I have the key all the way over. Suddenly though something changes and then it runs flawlessly. It appears to be a short of some type. I've wiggled and cleaned all
Exposed wires and connections but havnt dived any deeper yet. Any suggestions?

If it has the little smart box, that thing has been known to cause issues. It controls the spark, and if it isn't getting good power for some reason, it could cause issues. Could also just be bad. If it doesn't have that box, then there really isn't anything in line with the coils that should cause problems, unless there is an issue with the kill wire---short, pinch, etc.

Thanks for the reply. My motor is an 09. It doesn't appear to have the smart box. I've taken the cover off and cleaned every connection and checked magnetos. Only thing left I could see causing the issue is maybe the key cylinder itself. When the key is in cranking position it has spark but in run position it has no spark. Could this be possibly a bad cylinder?

I would check the key switch and ground wiring to magneto(white wire) when in run or on there should be no ground on that wire. when in off it should go to ground and kill the motor.


http://www.mudbuddy.com/MB%20wiring%20d ... Kohler.pdf

I checked the white wire that goes to the magneto. It is uninterrupted does not ground out anywhere. The other white wire that comes out of that spot goes to the trim motor switch and I unplugged it to be sure that switch isn't grounding it. I also replaced the key switch and that did not fix it. The motor still starts up and will run as long as the key is in the crank position but as soon as you let it off Into the normal on position it dies. I'm at a loss

Does your have that advance spark module? look at that, disconnect the oil pressure switch that could be grounding your coils

looking at wiring diagram the oil pressure switch is the easier to check just disconnect the wire to it if it runs - that the snufu.

I did disconnect the green wire which appears to be the oil pressure switch. It goes to a sensor on the top of the motor right behind the carb. I also disconnected the kill switch on the football.

Disconnect the kill wire at the coil and see if it runs.

Which one is the kill wire at the coil?

Spade terminal plugged into the coil.

Ok. Going to the coils there is a white red and black wire. I traced the black wire and it connects the coils together then it goes the the frame and grounds out. I disconnected that one and had no spark at all. Is that the correct wire?

You sure you don't have the smart box? Little black plastic box screwed to the blower housing?

I don't know wire colors. I use a volt meter. If you know how to use a meter, the kill wire would be the wire that goes to ground in the "key off" position, should be nothing in the "start" or "run" position.

There is one box that's attached to the housing cover. It has 3 wires that go to it. It looks like a purple and 2 whites. Is this the magic box you're talking about?

Probably, and if it has that box, it could be what's causing your issue. I believe there is a troubleshooting section for that thing in the service manual. I believe you can still download the service manual for free on kohlers website.

So the black box that's on the housing is the regulator rectifier. Is this the part that causes problems? My understanding is that it has to do with the alternator.

What I'm talking about would be on the other side of the motor.

Key switch possibly?

I do not have that box on mine. I verified that the fuel shutoff has power and is working and replaced key switch. Does anyone have any ideas on how to hit wire it and bypass the key switch all together?

How many wire are connected to each coil? Besides the plug wire. If there is only 1 disconnect it and try it, but if that is the case it will "kill" with the switch.

Each coil has 3 spades and has a white red and black wire connected in addition to the spark plug wire. The black wires are connected to each other then they go to a screw and ground out. I took the black wire loose from the screw and it will not spark at all. The red terminals are connected with a jumper between them then they go towards the switch. The red wire merges with another red that goes to the fuel shut uff solenoid. The red then goes down and splits at what I beleive is a diode possibly. After they split one goes to the starter terminal on the switch and the other goes to the one below that. I believ that one is rectifier based on the wiring diagram.

The are 2 ignition 12v inputs in the ignition. 1 of them is 12volts during cranking only for a lower ignition timing while cranking. The other is 12v when triggering the run position and uses more timing while
Engine is running. The diode keeps them working together with the fuel shutoff solenoid. My guess is you have 12v during cranking but dont have your 12v to the run position wire when u let off key and back to run...

That makes sense will. Thanks. I will put a voltage meter on them in the morning and see which wore is which. I'm guessing the red is cranking and white is run but that's only a guess. What is the diode you speak of and should I go ahead and replace it or is there a way to test it. I havnt been able to find literature on it. Thanks.

So I believe it's fixed. I tested the diodes and one let current go through it both directions. I cut it out and motor ran right. Going to go buy a diode tomorrow and put it back in. Thanks all for the help!

Think of a diode as a check valve, sometimes it fails open and others shorted.

A faulty Diode it was. I put a new one in it this afternoon and it's running great.

Good deal

Multimeter saves the day Again! My favorite tool in the Shop!

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My favorite is a power probe,,, multimeter is a close second

I broke my power probe