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Kohler ch20 on a 20 hp Sunstar


John2189

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John2189

Last year about this time one of the coils went bad. I put two new kohler oem and kohler boxes bought from an eBay seller   Anyway after mowing for 2 hrs the last couple passes, it started missing on one cylinder. I went to the garage and pulled the spark plug wire on one cylinder and it didn’t make any difference. I put it back on and cut the throttle to 1/2 and it ran fine. Pulled the wire and it started missing. The same at idle. 
Why would it run ok at 1/2 throttle and less but not at full throttle no spark. 

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Ronald Hribar

Kohler OEM and boxes ?

two new coils?

you put the coils on this year or last year?

if last year . Did it run okay then

or is this when everything started?

maybe it cannot supply enough fuel at full throttle 

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John2189


new coils last year ran great last summer, unlit now 

 

pulled choke, no difference 

 

 

 

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Brettw

This is just a thought.  I'm not sure how you set the clearance on the coils to the flywheel, but if one was a bit too large of a gap and perhaps now, a bit more tired after a few years of use, it doesn't create the proper spark when at higher RPM's?  I have always set mine with great precision; a business card between the flywheel magnet and coil, tighten 'er down and send it.  Or, maybe just a bad or tired coil, even though NOS Kohler?  Lastly, have you checked the plug itself, or are you using a spark tester? 

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PhanDad

What were the part numbers of the "new" coils you purchased on eBay?  Many times eBay NOS parts have been superceded; they might be one of the early coils that had heat related intermittent failure issues.  

In 2017, Kohler part number 24 584 45-S was the "newest" "good" coil.  This graphic shows the part numbers it replaced, some of which had issues - 24 584 01 for sure.   

IgnModule2458445S.JPG.31465e706f4d1c2bb260018047413d2e.JPG

The 24 584 45-S coil has since been superceded to 24 584 201-S.  

 

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John2189
18 minutes ago, PhanDad said:

What were the part numbers of the "new" coils you purchased on eBay?  Many times eBay NOS parts have been superceded; they might be one of the early coils that had heat related intermittent failure issues.  

In 2017, Kohler part number 24 584 45-S was the "newest" "good" coil.  This graphic shows the part numbers it replaced, some of which had issues - 24 584 01 for sure.   

IgnModule2458445S.JPG.31465e706f4d1c2bb260018047413d2e.JPG

The 24 584 45-S coil has since been superceded to 24 584 201-S.  

 

It said it was the 24 584 201S coils

i don’t remember what i set it at but I m sure it was to spec

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John2189
2 hours ago, Brettw said:

This is just a thought.  I'm not sure how you set the clearance on the coils to the flywheel, but if one was a bit too large of a gap and perhaps now, a bit more tired after a few years of use, it doesn't create the proper spark when at higher RPM's?  I have always set mine with great precision; a business card between the flywheel magnet and coil, tighten 'er down and send it.  Or, maybe just a bad or tired coil, even though NOS Kohler?  Lastly, have you checked the plug itself, or are you using a spark tester? 

I just pulled the plug wire. I will check the plug and use the spark tester for the coil tomorrow 

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Bill725
13 hours ago, John2189 said:

I put two new kohler oem and kohler boxes bought from an eBay seller

What do you mean by "Kohler OEM and Kohler boxes?" If the box is the Digital Spark Advance Ignition (DSAI) box, Kohler had issues with them and have been replaced with standard non spark advance MDI ignition modules. My understanding is the DSAI modules came on higher HP engines. Not sure they came on 20HP engines.

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John2189
1 hour ago, Bill725 said:

What do you mean by "Kohler OEM and Kohler boxes?" If the box is the Digital Spark Advance Ignition (DSAI) box, Kohler had issues with them and have been replaced with standard non spark advance MDI ignition modules. My understanding is the DSAI modules came on higher HP engines. Not sure they came on 20HP engines.

Sorry for the confusion but I meant the cardboard boxes they came in. 

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John2189

Tested the spark this morning. Everything seems ok. Did not have time to get it hot, so maybe when it gets hot it stops working 

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ShaunE

Not trying to steer you in the wrong direction here but I went down this road off & on for a couple seasons. Ultimately my problem was a partially plugged emulsion tube in the carburetor. However my symptoms started within seconds of a cold start. Now it’s the first place I go if the symptoms reappear. There are many ignition problems that end up being fuel/air problems.

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John2189

Thanks. I do know that the electric solenoid on the carb sticks   But when that happens, it won’t start at all 

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Bill725

If this is a newer engine and you remove the carb, make sure to check for a small aluminum welch plug install over the jet adjustment and remove. Obviously remove the jet to clean.

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John2189
57 minutes ago, Bill725 said:

If this is a newer engine and you remove the carb, make sure to check for a small aluminum welch plug install over the jet adjustment and remove. Obviously remove the jet to clean.

Ok thanks I’ll look for it 

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SmilinSam
20 hours ago, ShaunE said:

. There are many ignition problems that end up being fuel/air problems.

One of those "drive you nuts" problems...

My prestige was dying out, missing and such after warming up . Fought that for 2 years. Finally got down to the end of things to try. Replaced the fuel line from the tank to the pump. Bingo!...fixed the problem...

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Tarheel
22 hours ago, John2189 said:

Thanks. I do know that the electric solenoid on the carb sticks   But when that happens, it won’t start at all 

 I spray carb cleaner into the solenoid then twist and move the plunger until they free up adding more cleaner as needed. I have a feeling that if the solenoid is gunked up, the jets in the carb may well be also .  BTW, I add carb cleaner and work the plunger until the cleaner comes out clear. This may take a number of tries.

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John2189

Ok started it up, ran great for about 20 minutes then started missing. Let cool down and it ran ok. 
tearing it down and have new coils on order. 

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hurleyii
1 hour ago, John2189 said:

Ok started it up, ran great for about 20 minutes then started missing. Let cool down and it ran ok. 
tearing it down and have new coils on order. 

This sounds identical to a problem I had on a Deer zero turn walk behind. I replaced everything ignition related except coils on engine and even tried fuel pump. Was very inexperienced at that time on small engine repair and finally went up to my Simp dealer. Told him what all deer had steered me to and what I had done and I got a smile and said the first place you should have started was fuel line. Told me to try draining my gas tank and see what happened. Long story short fuel line was plugged partially and engine was starving for fuel and the longer it ran the worse it got till it wouldn’t stay running. 

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John2189

One cylinder good and one not firing. Plus I pulled choke with no difference 

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hurleyii
8 hours ago, John2189 said:

One cylinder good and one not firing. Plus I pulled choke with no difference 

This is going to sound silly maybe. I’m not sure I buy it myself, but it popped in my head. 
 Have you done a compression test immediately after it shuts down, when engine is super hot still?

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John2189
23 hours ago, hurleyii said:

This is going to sound silly maybe. I’m not sure I buy it myself, but it popped in my head. 
 Have you done a compression test immediately after it shuts down, when engine is super hot still?

I did a compression test cold and they were both 150lbs. 

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hurleyii
9 hours ago, John2189 said:

I did a compression test cold and they were both 150lbs. 

Do one when it’s hot! You could find it’s different. Not sure what that would suggest though. 

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I chased one of those Gremlins a fews years back.  It too was intermittent, and I think I had the carb off twice, replaced the coil on the side that coincided with the off color plug.  Finally found the problem mowing at night, and could see the spark jumping to the tinwork through the spark plug boot.

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1 hour ago, acken said:

I chased one of those Gremlins a fews years back.  It too was intermittent, and I think I had the carb off twice, replaced the coil on the side that coincided with the off color plug.  Finally found the problem mowing at night, and could see the spark jumping to the tinwork through the spark plug boot.

Thanks 

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On 6/12/2024 at 7:53 PM, acken said:

I chased one of those Gremlins a fews years back.  It too was intermittent, and I think I had the carb off twice, replaced the coil on the side that coincided with the off color plug.  Finally found the problem mowing at night, and could see the spark jumping to the tinwork through the spark plug boot.

Working on cars chasing a misfire we would turn shop lights off and mist engine with water to check plug wires for a short . You can then see any week spots that are grounding out before spark plug.

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