kohler won't stop

[curved-wood]

I have a Kohler 25 hp on a lt40 that does not want to sop when I turn the key off. Any idea where I should start my check-up ?

[dgdrls]

Help! My Kohler 25HP won't shut off! | Tractor Forum - Your Online Tractor Resource and Community

see if this can help you.

good luck

D

[47sawdust]

Fuel solenoid

[Ben Cut-wright]

I have a Kohler 25 hp on a lt40 that does not want to sop when I turn the key off. Any idea where I should start my check-up ?

How have you been stopping it since the problem?

Does it run poor when you shut the ignition off or does it continue to run well?  The isolation diodes can prevent killing one or both coils if open.  Don't know if yours had the diodes in the module or the line.  Easily tested with a test light.

[farmfromkansas]

Does it help if you throttle down to slow idle?

[curved-wood]

I have a Kohler 25 hp on a lt40 that does not want to sop when I turn the key off. Any idea where I should start my check-up ?

How have you been stopping it since the problem?

Does it run poor when you shut the ignition off or does it continue to run well?  The isolation diodes can prevent killing one or both coils if open.  Don't know if yours had the diodes in the module or the line.  Easily tested with a test light.

It does run very poor when I shut off the key. Horrible to ear

[curved-wood]

Does it help if you throttle down to slow idle?

No it is not stop if I engage the motor ( which give some throttle ). If I turn the key back on the motor run smooth again. After a few tries it finally stops.

[luap]

I believe Ben C is pointing you in the right direction. After you shut it off wiggle the wiring harness to see if it shuts off. Sometimes the diodes are connected with crimp on connectors and lose connection.  

[VooDooChikin04]

It could also have hot spots in the cylinders which is igniting fuel without a spark, we always called it "dieseling". Sometimes an old air filter that's falling apart and sucking pieces into the engine can cause this.

The wrong octane rated fuel can too but I wouldn't expect to see that on a small engine.  The timing also can't really change on these motors either unless you've sheared the key, and the flywheel has advanced a little, then you'll get some run-on when the key is off. 

I've seen oil additives cause this as well, such as marvel.

Otherwise a faulty keyswitch which is allowing power to the coils when off, or other wiring like previously mentioned.  I think that's about everything you could possibly check.

[curved-wood]

Thank you for the suggestions. I dont know why but problems happen only when there is a rush ;D Right now is a total rush for cedar.    Anyway... I replace the connector on the coil and it worked for one time but now it return to the same. Could I disassembly the coil to try to clean the connector or those are all sealed?

[curved-wood]

The timing also can't really change on these motors either unless you've sheared the key, and the flywheel has advanced a little, then you'll get some run-on when the key is off.

The motor seems to clack a little, could it be the timing ? If so is it complex to ajust or I have to send the motor to the specialist ?

[dgdrls]

Other than shutting down,
How does it start??
You mention it runs fine with the key on

If this is your only problem, don't start chasing maybe's,   You have to make sure the keyed circuit is cutting power to the coil(s) consistently first.
Also, check for frayed wires,  I recently found a frayed wire going to one of my coils, when I was troubleshooting a charging problem.
Charging problem

If you can work a test light and a volt meter, I would pull some of the shielding and look at the wiring first.
And while you're in there blow out any sawdust you find especially around the cylinder(s).

D

[curved-wood]

Other than shutting down,
How does it start??
You mention it runs fine with the key on

If this is your only problem, don't start chasing maybe's,   You have to make sure the keyed circuit is cutting power to the coil(s) consistently first.
Also, check for frayed wires,  I recently found a frayed wire going to one of my coils, when I was troubleshooting a charging problem.
Charging problem

If you can work a test light and a volt meter, I would pull some of the shielding and look at the wiring first.
And while you're in there blow out any sawdust you find especially around the cylinder(s).

D

So if I understand wright, I should have a signal between the small black wire and the coil when I turn the key off ?

[jb616]

The timing also can't really change on these motors either unless you've sheared the key, and the flywheel has advanced a little, then you'll get some run-on when the key is off.

The motor seems to clack a little, could it be the timing ? If so is it complex to ajust or I have to send the motor to the specialist ?

Could it be poor fuel as well?  If it is "clacking" when running it could be spark knock or detonation which also causes the "dieseling"on shut off. Try a tank of premium fuel?  just an idea.

[VooDooChikin04]

The flywheel key can shear, timing advances a couple degrees, runs awesome... But runs hot in the cylinders and diesels when shut off. I've watched it happen. So its a possiblity.  Timing is non adjustable on Kohler commands as far as I know without getting an aftermarket pickup or flywheel with different key timing. 

[luap]

On a small engine the electric current for the coil is provided by the magnets in the flywheel inducing the current for the coil. The key switch grounds out the coil to shut the engine off. If there is break in that ground wire or if it is disconnected somewhere the engine will not shut off. An engine with an external coil gets its power through the battery/ keyswitch and the keyswitch connects or disconnects the power to the coil. No grounding of the coil takes place. 

[curved-wood]

On a small engine the electric current for the coil is provided by the magnets in the flywheel inducing the current for the coil. The key switch grounds out the coil to shut the engine off. If there is break in that ground wire or if it is disconnected somewhere the engine will not shut off. An engine with an external coil gets its power through the battery/ keyswitch and the keyswitch connects or disconnects the power to the coil. No grounding of the coil takes place.

so where should I start testing ?
When I turn off the key the motor is like running on only one cylinder and has a very low rpm.

[VooDooChikin04]

I've also had those small key switches go bad where they don't stop contact internally. Also recently my tractor which uses a cheap small mower type key switch had corrosion across the terminals on the backside and was arching across. Also need to check that out.  

Basically, my gut tells me you have one of two problems based on everything I've read from all the replies here. 

1: motor keeps running due to hot cylinder for whatever reason so it diesels on with its own source of ignition.
Or
2: your system is not stopping a coil from receiving power when the key is off, so it keeps on firing and chugging away.  

As far as when to start? If it was mine, id start at the key switch. I'd use a multimeter to determine if if it cutting juice when off. Then id move to the coil wiring to see if one is still receiving power when the key is shut off.  Next I'd look for chewed or frayed wires where power is able to still reach the coil.  

If you don't feel comfortable or do not have the knowledge of using a multimeter, watch some YouTube instructional videos, or find a friend, or ultimately visit a small engine repair place. Sometimes just paying the repair bill saves so much time and frustration.

That said, there is a lot of knowledge here and everyone is willing to help!!

[luap]

A year ago I repowered a compact tractor worn out Onan engine with a Briggs Vanguard. Upon request Briggs provided me a troubleshooting guide and a wiring diagram that showed wire colors and connections. So you should start by reaching out to both WM and Kohler. There are free PDf format manuals on google. That is where I would start my testing. Otherwise if you want to dive into it, start removing panels to expose the back of the keyswitch so you can identify the connections to test them. Each tab on the keyswitch may have a raised letter to identify the connection. B for battery, S for starter, G for ground, etc. It's a process of elimination. My number one rule of troubleshooting is not to replace a part until I have verified it is faulty. Here you are going to get lots of opinions but you need to start with verified information from the manufacture.

[Ben Cut-wright]

A year ago I repowered a compact tractor worn out Onan engine with a Briggs Vanguard. Upon request Briggs provided me a troubleshooting guide and a wiring diagram that showed wire colors and connections. So you should start by reaching out to both WM and Kohler. There are free PDf format manuals on google. That is where I would start my testing. Otherwise if you want to dive into it, start removing panels to expose the back of the keyswitch so you can identify the connections to test them. Each tab on the keyswitch may have a raised letter to identify the connection. B for battery, S for starter, G for ground, etc. It's a process of elimination. My number one rule of troubleshooting is not to replace a part until I have verified it is faulty. Here you are going to get lots of opinions but you need to start with verified information from the manufacture.

Recognizing nomenclature and having diagrams in hand will not ensure competent testing or result in comprehensive interpretation of the results.  One must be able to apply what diagrams and schematics depict to the actual working of the components. Failing this ability, opinions on what to test and the results of experience can be helpful. 

"A process of elimination" can also dictate replacing a component that is otherwise impossible to find faulty. 

The OP asked for assistance while providing only a description of the behavior.  There are a limited number of causes for the fault he described.  Replacing parts wasn't promoted.  Testing using simple tools should resolve his problem.
 
The description the OP gave indicates he isn't chasing a fuel problem.  Therefore, some ignition source is the reason the engine will not shut off.  Experience would quickly determine whether the engine was dieseling or that only one cylinder was running properly.  If dieseling is suspected, quickly opening the throttle to wide open will kill the engine.  

The OP states his engine does not stop when he engages the blade but does eventually stop when he cycles the key switch.Testing for ignition spark can be done by several methods.  If spark is not extinguished at key-off, testing the few points of interest is simple and requires only basic test tools. 

[Remle]

Here is where I would start, google this for the kohler manual: /www.kohler-engine-parts.opeengines.com/index.php?main_page=document_general_info&products_id=34596
Go down to, Kohler Command Pro Horizontal Twin Service Manual and open it up. Print off pages 35/36. ( wiring diagram/ connector identification table)
If grounding is good the engine should stop when the key is turned off.
1)   Check the key switch for continuity to ground.
2)   Remove the front cover and check the ignition kill circuit, Item D to U to AK of the key switch for continuity.
One additional thought, if the fuel shut off solenoid is not closing it may try to run from the internal cylinder heat, so with the key off check for power at location X. Their should be no power with key off.

Hope this helps or post back with your results.

[Gary Davis]

Mine did it to and it was the fuel shut of it is on the control side of the motor  I bought a new valve I was able to replace it by trimming abou a 1/4 in  of the shroud  you might be able to clean the old one

[luap]

This tool would help you determine if it is shutoff problem or the dieseling problem.
Amazon.com: Oregon 42-031 Spark Tester, Black: Garden & Outdoor. or google inline spark tester

[dgdrls]

Curved-wood,

does the motor have a carburetor or, is it fuel injected??

D

[curved-wood]

If dieseling is suspected, quickly opening the throttle to wide open will kill the engine.

I am still doing some test. Opening the throttle with key at off didn't change anything. 
I have tested the current between the starter and the coil, and in an out of the coil and everything is OK. The engine run correctly on full power. The valves are noisy a bit but not too bad
Is there a way to test if the problem is the ignition switch ?