Kohler fires on start, not on run

[smokediver]

My scag turf tiger, 20 hp Kohler just quit yesterday while mowing.
It will fire when starting, but when I release the key to the run position it dies.
I'm pretty certain it's an ignition problem because if I hit start again before it dies (I know, hard on the starter) it will pick up again.
I've checked fuses , relays, and wires all seem good. I even swapped out the ignition switch with a known good one, no luck.
A couple days ago I noticed it was sputtering once in a while when mowing.
Would it start on battery and run on the alternator? If so a bad alternator/stator, or regulator would be logical.
Don't some stators have one set of coils for battery charging, and another set for ignition?
Any input or suggestions appreciated.
Thanks.

[Restrorob]

Without any model/serial numbers posted all I can do is guess, Behind your control panel you should have two relays. Swap the relays around and see if it stays running. If so another function most likely wont work, Pick up one new relay then swap it in until everything functions properly.

[smokediver]

Hey Rob.

Sorry I haven't got the numbers yet, been in the road about 15 hrs a day, and at work now.
There's only one relay behind the control panel and it is for the blade clutch. It clicks when the blade pto switch is thrown.
There is another one on the back of the engine for the starter, but it only engages the starter: one wire from the switch, one from the battery, one to the starter solenoid, and a ground.
What do you think about the stator theory? Are there separate coils for the ignition and battery charging? I changed one before on an older Kohler that wouldn't charge, but did run, and I'm pretty sure it was that way. I just wanted to be pretty sure before I pulled it cause it's gonna be a booger. I think the engine will have to come OUT before I can remove the flywheel cover. It's a "turf runner" with the plastic grass catcher on the top/back and the engine underneath.

[Restrorob]

What do you think about the stator theory? Are there separate coils for the ignition and battery charging?


There are separate coils for the ignition system and a stator for the charging system, But.... They are non related, The stator has nothing to do with ignition.

Does your engine have a SAM ignition module mounted on the flywheel cover as below ?


http://i107.photobucket.com/albums/m314/Restrorob/Kohler/CH/CHSamBox.jpg

[whoopassonthebluegrass]

Does it TRY to start? If it does, but can't, it's either spark or fuel delivery. Does choking the motor cause any sort of change?

[smokediver]

Yes, Rob, I believe it does have one of those. I was looking at it and thinking it was in an odd place for a voltage regulator.

[topsites]

The only way I know of to test a relay is to replace it with a good one,
then if your problem persists you have a spare, but don't assume on this.
Because they all "look" good lol

Yes I realize they cost like $20 each but I buy one here, one there, now some years later I have a small collection of these :)

Peace out

[MowerMedic77]

The only way I know of to test a relay is to replace it with a good one
http://www.autoshop101.com/forms/hweb2.pdf
The last few pages have some test procedures

[smokediver]

Does it TRY to start? If it does, but can't, it's either spark or fuel delivery. Does choking the motor cause any sort of change?

It will start, but as soon as the key is released to run it dies.
If I bump the starter before it completely stops it will firre again.
It's ignition not fuel, I'm 100% sure, just trying ot figure out what would cause that sort of issue.

Rob, or anybody else,

Eng Model # CH22S Mower Mod # STR-22CH

Eng Serial # 2616915677 Mower Serial # 21761012

Thanks again for your help

[smokediver]

Rob,

What does that SAM ignition module do?
Could it cause this problem? It definately has one, exactly like the picture.

Thanks

[VegetiveSteam]

If it runs with the key in the start position but dies when you let off of the key your SAM module is working just fine. You've got a bad diode in the run circuit. The SAM module and fuel solenoid need to have power to them in both the start and run modes. When you turn the key to the start position the run position goes dead because they are two seperate circuits. Both circuits have diodes in them to keep from backfeeding voltage from one circuit to the other. When the diode goes bad you get no voltage. Go to either the fuel solenoid or the SAM module and disconnect the red wire. Take a test light or volt meter and simply turn the key to the start position and check for voltage. You should be reading battery voltage. You can check at either place because both the SAM module and the fuel solenoid are in the same circuit. I'm betting you only find voltage there when you turn the key to the start position. The replacement diode is Kohler part number 25 755 31-S. To find it start at the fuel solenoid and just follow the wire back until it y's off and that is where the start and run diodes come together. If you don't have a Kohler dealer close you can go to Radio Shack or some other electronics store and get av5A, 800PIV diode. Cut the old one out and solder in the new one. Make sure the striped end is toward the junction of the two circuits.

[smokediver]

Well now, that makes pefect sense.
And I would've pulled my hair out trying to find that.
Thanks for the info V/S.
I'll check that today

Thanks, SD

[smokediver]

:laugh: I FOUND IT!!! :clapping:

It was a broken wire coming out of the fuse holder in the control panel!
I had checked the fuses, and they were good, but didn't check the wire behind them.
I also discovered it does need BOTH relays to run, the one in the control panel is power to EVERYTHING.

Thanks for all the input guys, really appreciate it!!

Smokediver