John Deere z915e 25hp Kohler sporadically dropping one cylinder unless kill wire on the coil is unplugged

[scott gibbs]

Hi, I have a z915e with a 25hp kohler. When my problem started the mower would start up and run fine but every once in a while it would just drop one cylinder. After a few minutes, or sometimes after shutting down and restarting a few times it would pick up the other cylinder and run fine again for a while before doing this again.

Now, when I start up the mower it is only running on one cylinder until I pull the kill wire off the back of the coil of the cylinder that is not firing. After pulling the wire off the coil, the mower runs fine for a while. So I made a toggle switch to the kill wire on the coil of the cylinder that drops out. So I start it up on one cylinder and then flip the toggle switch( which is the same as pulling the kill wire off the coil thats not firing), and it runs on both cylinders, but now, every once and awhile the other cylinder drops out. After a few minutes, it will backfire and pick up both cylinders and run until the next time it decides to drop a cylinder. Sometimes I can get off the seat and back on and it will run fine again, but I have tried bypassing the seat safety switch and that has no effect on the issue. The issue is not as bad as it was before but I really need to find the problem and fix it without keep just replacing parts one after another with no solution.

First I replaced spark plugs, then one coil, then I replaced the kill wire coming from the engine wiring harness, then I replaced the engine wiring harness, now john deere mechanics are telling me to replace the main wiring harness which is over 500.00. I have also checked and cleaned all negative and positive connections, cleaned stator magnet and coil connections, switched out the key switch with another key switch.

I have run out of ideas, thanks for yall's input!!

 

[bertsmobile1]

Hi, I have a z915e with a 25hp kohler. When my problem started the mower would start up and run fine but every once in a while it would just drop one cylinder. After a few minutes, or sometimes after shutting down and restarting a few times it would pick up the other cylinder and run fine again for a while before doing this again.

Now, when I start up the mower it is only running on one cylinder until I pull the kill wire off the back of the coil of the cylinder that is not firing. After pulling the wire off the coil, the mower runs fine for a while. So I made a toggle switch to the kill wire on the coil of the cylinder that drops out. So I start it up on one cylinder and then flip the toggle switch( which is the same as pulling the kill wire off the coil thats not firing), and it runs on both cylinders, but now, every once and awhile the other cylinder drops out. After a few minutes, it will backfire and pick up both cylinders and run until the next time it decides to drop a cylinder. Sometimes I can get off the seat and back on and it will run fine again, but I have tried bypassing the seat safety switch and that has no effect on the issue. The issue is not as bad as it was before but I really need to find the problem and fix it without keep just replacing parts one after another with no solution.

First I replaced spark plugs, then one coil, then I replaced the kill wire coming from the engine wiring harness, then I replaced the engine wiring harness, now john deere mechanics are telling me to replace the main wiring harness which is over 500.00. I have also checked and cleaned all negative and positive connections, cleaned stator magnet and coil connections, switched out the key switch with another key switch.

I have run out of ideas, thanks for yall's input!!

Pull the kill wires of each coil
If it runs fine like that replae both coils.
There is a diode embedded in both of them that prevents then talking to each other via the kill wires
Not a very common problem with Kohler coils but does happen.
No possible repair both coils will need replacing .

 

[scott gibbs]

So I tried that, and it's working fine just takes a min to cut off because it's only relying on fuell shut off, but I can't remember why I didn't have both unplugged before... there was a reason.... mabe it was still doing the same thing after running awhile. I can't remember. But I'm about to go mow with it like this to see if I can get it to mess up or not. Let ya know what it does. Thanks

 

[bertsmobile1]

Remember thiis is not a fix just a diagnostic test
B & S put the diodes in the loom so they are replaceanle
Kohler use much better diodes but unfortunately they are embedded so it is new coils time
And you have to relace both of them .

 

[scott gibbs]

So I tried that, and it's working fine just takes a min to cut off because it's only relying on fuell shut off, but I can't remember why I didn't have both unplugged before... there was a reason.... mabe it was still doing the same thing after running awhile. I can't remember. But I'm about to go mow with it like this to see if I can get it to mess up or not. Let ya know what it does. Thanks

So, I mowed 1 1/2 acres without any problems with both kill wires unpluged. The only thing is that now the hr meter did not record any of the time I was just mowing. The same amount of hrs are showing as when I started mowing. It should have showed about 30 min. So if I understand you correctly what I need to do is replace the other coil. Correct?

 

[bertsmobile1]

If you replaced one, then yes replace the other one
The coild have a Hall effect timng chp in them that replaces the points ( remember them ?)
The chip measures the tiny change in coil voltage and is very easily damaged .
I have never gotten away with just replacing the coil that was not firing properly

 

[scott gibbs]

Ok, I will try putting a new coil on. I'll let you know how that goes. Thanks!

 

[scott gibbs]

Well, hot damn!! I put the new coil on and it ran perfect!!!! Thank you so much!!!!!