Kohler Cutting Out - Carb cleaning?

[Digger 258]

I was trenching for a couple of hours, and every once in a while the engine would just up and die. She would start right up again and run fine for another stretch. I thought maybe I was over heating. I let it cool for a while and when I came back, she would only start and run on full choke. So i finished the job, and put her away until I could get to a computer. Moved her into the garage today to take a look, but before I do I thought I'd ask you all what you think. I'm thinking the carb needs to be cleaned. Maybe it could be something as simple as a fuel filter or something though. Any thoughts?

Thanks
Dan
PT-425 with Kohler 25.

 

[Marks481]

3 theories:

1. Vapor lock in the fuel pump or fuel line. When the engine shut down, take a look in the gas tank and see if their are vapor bubbles coming from the inlet inside the tank.

2. Tank vent is clogged so you are drawing a vacuum on the tank. Open the tank, and listen for air hissing in as you open it.

3. Fuel pump is going bad, and condition gets worse when it gets hot (this one is a stretch).

Your description makes it definitely sound heat related, and since you needed full choke to restart a hot engine, that suggests fuel starvation.

If your fuel filter is clogged, you should be able to tell just be looking at it (assuming it is the typical clear plastic cheap small engine filter like mine).

 

[MossRoad]

The choke limits the air. If you need full choke, doesn't that mean there's too much air and not enough fuel? So check the fuel filter first.

 

[Billrog]

No.2 of what tmarks11 said loosen the fuel cap and see if it still happens.

 

[Digger 258]

Thanks to all so far, and here's where I am at this point.

Pulled the air filter out, and started the engine with full choke. Slowly took choke off until it sputtered but kept running. Sprayed carb cleaner around the base of the carb. On the passenger side (ha!) the engine revved slightly, so I assumed I had an air leak. So I tightened the carb mounts, but there was really no difference.

That got me to thinking - what about that electric thing that I think shuts the carb down when I turn off the key? I put my finger on that and felt it click when I turned the key on and off, but not consistently.

So I pulled the carb off, and pulled that thingy off the back of the carb. Hooked that thingy up to it's power wire and ground. It "plunges" if I hold the key switch just right, but not consistently. I am beginning to think I have a bad key switch. Or maybe I need to clean it, since I was in some pretty good mud. Maybe since the switch was letting ignition run, but not that thingy, which meant I needed choke to run right (since that thing starves fuel or air somehow.) SOrry for the hurried update - have to tuck the kids in before I crack at this some more.

Bottom line, I'm thinking ignition switch. Thoughts?

Thanks again.

 

[MossRoad]

Is that a fuel shutoff solenoid? I don't have my carb in front of me... :laughing:

 

[rswyan]

I'm in the process of cleaning the carb (Walbro) on a Kohler Magnum 18 in Simplcity CFC 18 (circa 1985 - 87)

I say "in the process" because I've had the carb off twice now ... and both times there's been black crud in the float bowl. I suspect fuel line deterioration after the filter.

Symptoms are the same as the OP's ... will only run with choke on.

Runs good after I clean it ... until more crud accumulates in the float bowl.

 

[Digger 258]

Yeah, I guess its a fuel shutoff solenoid. I suppose I'm in for cleaning the carb out as well since I have it off. I still suspect the key switch though, since the fuel shutoff solenoid plunges when I wiggle the key (but the headlamps don't go out when I jiggle the key . . .)

 

[MossRoad]

I think its a fairly common key switch. I got one a couple months back at Rural King for about $10 as I recall. So even if its not the problem, its not too expensive of an experiment.

 

[Digger 258]

I got the switch out of the dash - that was more of an origami project than I expected! I also took the carb apart, but it didn't have a speck in the float bowl, so I held off on spraying it out and just put her back together. I'll try replacing the switch first tomorrow and see where that takes me. I was worried that the switch would be a rare breed - but MR has me optimistic that Napa will have it . . . fingers crossed - I have a big project planned for this weekend installing drainage.

By the way, last weekend I dug about a 100 yard trench in really soupy mud. Of course, I dropped the right side tires into the trench and buried the PT beyond the top of the wheels in soup. I was almost able to crab out, but after making it worse I had to use the truck for a quick snatch. Turf tires didn't help, but in reality I should have been stuck more often if not for the hydraulic steering and ability to push myself up with the mini hoe. First time for me getting stuck other than in snow drifts. I am considering a more aggressive tire when I wear these out.

Regards