# Kohler Engine Problem



## ironhead (Mar 25, 2012)

I have a Kohler Command 27 hp. Model CV740S. The issue I am having and have had since it was new is that at random times the engine will not fire till I let off the key. I even have a video showing this. The mower is an 2004 model and I bought it brand new. This is the only issue I have had with the engine. The Simplicity dealer put a new key switch on it a few months after I bought it. Last spring they took out a diode or something. Kohler told them there were two diodes in the system. I think they said one was for run and the other for start but one of them wasn't needed. I thought the problem was solved after that. But this past weekend I tried at different times all day Friday, Saturday and Sunday trying to start the engine. I went to load it on the trailer today to take it to the dealer and the darn thing started!!!! This is why it is so hard to diagnose I guess but this has been an issue since it was new. Has anyone else out here experienced that problem and if you have what have you done to fix it.


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## Fedup (Feb 25, 2014)

I don't know the details of your machine, as I don't usually work on lawn and garden machinery. I do, however, get stuck with one on occasion, and usually spend more time trying to learn the system than actually finding the problem. Most L&G engines of this type(but not all) use a simple permanent magnet type coil with a single wire "kill" system. When this wire is grounded, the coil doesn't produce spark so the engine dies. (or won't start) How this wire gets connected to ground varies from machine to machine, but it's usually tied into the operator aggravation circuits as well, providing multiple opportunities for intermittent problems. This system often has a ground circuit within the keyswitch which provides the ground when in the "off" position, and breaks this when in any other position. That's probably why your switch was replaced once before. 
You might try locating the "kill" wire from the coils(if you do indeed have this system) and isolating it from the switches entirely. The engine should then start whenever it's cranked, and won't shut off until you ground the wire. I'm not suggesting this as a solution, but it may give you a path to begin isolating possible problem circuits one at a time.


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## jhngardner367 (Apr 5, 2011)

Ironhead,what make,and model # is the tractor ?
It sounds like a problem with the wiring of the tractor,not the engine .A safety switch,etc. out of adjustment.
It could,possibly , be the armature(coil) having an intermittent short,to ground,also.


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## ironhead (Mar 25, 2012)

It is a Simplicity Zero Turn Stallion mower. It is ZT 61, meaning zero turn 61" deck. The model # is a CV 740S. I have been through Simplicity. Simplicity says it is a Kohler problem. Kohler says it is a Simplicity problem. I think it is a Kohler problem. All switches have been checked by the dealer so I am told. All wiring harnesses have been checked by the dealer, so I am told and nothing has checked out bad. 

I took it back to the dealer yesterday and told them I didn't want it back till it was fixed. I have done that once before and they thought, as did I, that it was fixed. Here is a link to a short video showing what is going on.

https://youtu.be/4UuSdmdl9ko

Ironhead


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## jhngardner367 (Apr 5, 2011)

Tell them to change the armature(coil),and make sure the kill wire is ok.
In the meantime, unplug the kill wire from the coil,and put on one you can touch to ground,if it starts.


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## bbirder (Feb 26, 2006)

I'd also like to see him put switch in run position and jump the solenoid. I'm not sure about those diodes in the circuit. I like the coil also.


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## bbirder (Feb 26, 2006)

I'd also like to see him put switch in run position and jump the solenoid. I'm not sure about those diodes in the circuit. I like the coil also.


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## ironhead (Mar 25, 2012)

Thanks for all the advice. I really do appreciate it. I sent them the video and here is their response:

The video definitely helps out, that looks different then I was expecting. Before when Mike and I did the diode, there was no spark while cranking and consistent spark as soon as you let off of the key. This almost looks like a bad ground, bad connection, bad coil, I'm not exactly sure. I will get this to the Kohler guys after the first of the year and hopefully they will point us in the right direction!

So he seems to be thinking along the same lines you are bbirder. We will just see how it goes. I know these people personally. They are good people. I don't want anyone to think they are trying to pull one over on me. They are just stumped and I know sometimes it happens. When the mower starts, it runs perfectly!

Ironhead


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## bbirder (Feb 26, 2006)

I dunno. I read it as he agrees with jhngardner367. John hit on the coil and/or grd. These things can be hard to track down sometimes. Just takes time. I don't think the dealer is trying to pull one over on you. Let's see what the manufacturer says after the first. Let us know. We don't like to be kept in suspense, as we all learn from these problems!


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## ironhead (Mar 25, 2012)

My apologies to jhngardner367. You are correct bbirder. He is the one that suggested the coil and ground. I took the ground wire loose from the chassis, along with 5 other wires on the same bolt before I took it back to the dealer. I cleaned contact surfaces the best I could and cleaned around the bolt hole and it still wouldn't start. I am guessing the ground they are talking about may be some kind of ground within the coil or some other component. But that is beyond my mechanical ability to find it, so that is why it is at the shop again.

I hope you all have a healthy and prosperous New Year. Thanks again!

Ironhead (Damon)


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## Fedup (Feb 25, 2014)

I'm not buying the bad coil theory at all. I suspect there are two coils, one for each cylinder. Chances of both having an "intermittent" problem at exactly the same time are too slim to measure. I believe the coil grounding circuit is the key here. The keyswitch evidently has been replaced once with little or no help. I suspect that switch is used on a great many machines with good success, so I have to go with the circuits being the issue in this case.


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## wjjones (May 28, 2010)

Sounds like a loose connection, or short to ground somewhere. Have you inspected all the wiring connections, and covers?


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## jhngardner367 (Apr 5, 2011)

It's good that the dealer has responded,this way. Many would not.
There were a few that I had in my shop,that acted this way,and some had bad coils,some had bad ignition switches,and some had wiring problems,or a bad safety switch.
ALL would run fine,once started, but checking each circuit takes time,and throwing parts at it,just wastes $$$.


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## RC Wells (Dec 26, 2008)

There are two areas to check in addition to the ignition, the seat safety switch, and on the side of the engine there will be a potted component with one or two wires clipped to the center of the potted area. That is the regulator. If it gets bridged with mud they will ground out the electronic ignition, if they burn out they will fail to pass current to the ignition, if the wire connector corrodes same problem, the ignition gets erratic.

There are also other safety switches to consider. The blade engagement switch and the neutral safety switch. Finding a bad switch is always a snipe hunt and requires a good multimeter to check impedance as the switch if flipped when it is disconnected from the electrical system.


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## jhngardner367 (Apr 5, 2011)

On mine(Also a CV740s) it has 2 coils,BUT,the kill wire is a single wire,that splits to 2 wires. 
The problem on mine,was that the armatures had developed hairline cracks(yes,both of them),and would,sometimes fail to fire.
Also,the kill wire was chewed by mice.
Rather than replacing the coils, I coated them in clear epoxy,and I haven't had a problem,since.
Some engines won't run,if one of the coils is bad,while others will run,but don't run well.

Also,Simplicity is noted for adding electronics,so it has to have a part from Simplicity,much the same as JD does.


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## ironhead (Mar 25, 2012)

RC Wells said:


> There are two areas to check in addition to the ignition, the seat safety switch, and on the side of the engine there will be a potted component with one or two wires clipped to the center of the potted area. That is the regulator. If it gets bridged with mud they will ground out the electronic ignition, if they burn out they will fail to pass current to the ignition, if the wire connector corrodes same problem, the ignition gets erratic.
> 
> There are also other safety switches to consider. The blade engagement switch and the neutral safety switch. Finding a bad switch is always a snipe hunt and requires a good multimeter to check impedance as the switch if flipped when it is disconnected from the electrical system.


Everything you have suggested has been done in the past or so I have been told. I have no reason to doubt them. The biggest problem is that Kohler is saying it is a Simplicity problem and Simplicity is saying it is a Kohler problem. The dealer will just have to keep my mower till it acts up and won't start and start trouble shooting it then.


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## wjjones (May 28, 2010)

ironhead said:


> Everything you have suggested has been done in the past or so I have been told. I have no reason to doubt them. The biggest problem is that Kohler is saying it is a Simplicity problem and Simplicity is saying it is a Kohler problem. The dealer will just have to keep my mower till it acts up and won't start and start trouble shooting it then.


Whoevers problem it is it shouldnt be yours. I hate it when they haggle that way meanwhile the customer/ owner gets stuck in the middle.


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## ironhead (Mar 25, 2012)

Just to update everyone who has been so kind to respond to this post. My mower finally started acting up. They pulled the kill wire and it started right up. From what I understand that isolated the motor from the chassis and therefore the problem was with the mower not the motor. But after running all the required tests for all the switches everything was getting the correct volts and so there was no issue with the wiring harnesses. So back to the motor they went and found a wire under the fly wheel somewhere that had been rubbing and it had rubbed a bare spot on it. They fixed that and the mower has not failed to start since. The mower is still at the shop, per my request, to see if it is going to act up anymore. Even though this seems to have fixed the problem, it still puzzles me that it would just do this sporadically. I could go out and start my mower and mow with it, put it up and the next week it wouldn't fire for nothing. It would seem it should quit firing when the wire rubbed. I can't see how it would rub after I shut the mower down to the point that it wouldn't fire the next time I wanted to use it. Anyway that is where we are. Have a great day and I hope this made sense.


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## RC Wells (Dec 26, 2008)

The wire must have been installed without the protective sleeve to keep it from rubbing through. It happens, and it causes intermittent ignition failure.


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## jhngardner367 (Apr 5, 2011)

It could,as RC Wells said,have been the kill wire,and had been installed "loose" causing it to rub .
After many years of gas,diesel,and small engine repair work, I often find it's a simple thing that causes a problem.
Glad they found it !


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