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model # is CH25S/ Family SKH725U1G2RA SER # 2829418121/SPEC#68613, 1998 model. replaced fuel line s, filter, plugs, checked all connections for ignition . Checked fuel solenoid. It shuts under load or not and wether I'm on mower or not. Its a scag turf tiger. engine does not smoke. Any ideas?

Thanks for the engine numbers, your engine has a Speed Advance Module, or S.A.M., also know as Smartspark, which is a real troublemaker for folks trying to diagnose engine problems. Many times the trouble is just corroded terminals on the back of the keyswitch, or other places, take a quick look and see. And let us know, if not we can go a little deeper.

ignition switch looks good and all other connections look good under dash

Well, it is a quick thing to look at. You need to determine what is at fault when it shuts down, spark, fuel or compression.
We can rule out compression, as it runs fine when it runs, but you need to see if it is fuel or ignition related, so keep with you an extra plug and a can of carb cleaner, and when it shuts down, see if will restart with a squirt of carb cleaner,


and pop on the spare plug, lay it against the block, and check for spark. See what that tells you.

It starts right back up, so its getting spark and fuel. Runs great until it warms up.

You're describing my mower to a T new coil pack, plug, carb is clean??? I read somewhere that muffler might be clogged or shear pin damaged if you find a solution, please post, this has been the hardest troubleshoot ive had in a while.THANK YOU:frown:

I wouldn't say it's a coil because, I think it would have to be both failing at the same time. Sounds like a fuel restriction. Fuel filter or maybe carb float. gregjo1948

Do a leak-down test to check for bad head gaskets.

If you have the SAM system, don't replace the coil. Replace the SAM module with the kit, which contains a new coil and module together in one unit,

Rivets said:

If you have the SAM system, don't replace the coil. Replace the SAM module with the kit, which contains a new coil and module together in one unit,

Click to expand...

Not saying not to do this if it's your problem. I have one in my shop doing the same thing. I went nuts trying everything to cure the problem. I finely did a leak down test and found a left side bad head gasket. The part that had me stumped and still dose is the shutting down.

Error

I know it says error, click on it anyway, it is an ipl for your engine.

Then clique the "select assy." then click ignition group.

Now ref # 12 is the S.A.M. unit, and ref #4 is for the coil, and note that there are 2, if there is a "kit", I have not come across one.

Also, to say to replace the S.A.M. unit would be kind of wreckless without trying to find out what the problem is.

But this system is unique, in that the SAM unit requires a minimum voltage to run, otherwise the coils will shut down, so you should get your hands on a multi-meter, and sit down and plan on putting some time in on figuring this out, someone here probably has a link to the Kohler mechanic's manuals, maybe they will put up the link.

Or you could go the other route, and replace parts that everyone suggests, which would require a big checkbook.

Or you could take it to a dealer, which would require bigger checkbook.

I suggested the quick look for corroded keyswitch terminals, because it is a common problem spot, and speeds up the process a bit.

But since a voltage drop could easily explain things, either by cutting power to the SAM unit or else the fuel shutoff solenoid, I would suggest the first thing that you do is a simple voltage test of your battery running, and check the alt output, and at the regulator, just to start things....

I've found the problem. I had checked all connections under dash and all of the safety switches, beside all the other things I've listed. I was looking at the Sam and noticed the wiring connector that connects engine wiring to dash wires. I cleaned
connector, plugged back together. Started engine and let it run. It ran past the normal time shuts off. I figured I would mow with it and to my surprise it kept running. I mowed about 2 acres with no problems. A very simple fix, but it took over a month of trouble shooting, replacing parts, doing research, and allot of aggravation. Thanks for all of the help.

A month!!!!!!

It looks like well under 2 days here!!!!!!

Or do you think you found it out on your own??????????

Sorry, the bad connection wasn't under the keyswitch!!!!!!!

I am getting old and everyone here hates me!!!!!

Can't you at least throw me a little crumb?????????????

If not, then tell me/us why!!!!!!

Dang, this is a tough crowd......

I mean, a new poster here poses a question about diagnosing his mower problems. And someone here does, and he won't even be polite enough
to recognize that he diagnosed the problem...... Well, I guess that I am the sucker here. Maybe we should stop trying to help folks...

Carsacw? any thoughts?

Fish said:

I mean, a new poster here poses a question about diagnosing his mower problems. And someone here does, and he won't even be polite enough
to recognize that he diagnosed the problem...... Well, I guess that I am the sucker here. Maybe we should stop trying to help folks...

Click to expand...

Well done Fish you most always have the correct answer. Please keep helping these poor people that do not have your experience.

Fish said:

I mean, a new poster here poses a question about diagnosing his mower problems. And someone here does, and he won't even be polite enough
to recognize that he diagnosed the problem...... Well, I guess that I am the sucker here. Maybe we should stop trying to help folks...

Click to expand...

Hey Fish, folks like you are my forum hero's. For every shun you know about, there are ten like me that will hang on every word and appreciates you and others sharing. I have the same engine and will clean my electrical connections. I always use DeoxIT, but is there a water resistant grease for use after its plugged back in?

I like your method of checking the free simple things first and going up from there.

Thanks
Harry

Had similar with a simplicity a tew years ago. It turned out to be vapor lock. removed the hood to test , then ran ok. Easy and cheap test,route fuel line away from heat source the best u can for time being. Then give it a try ,if it does not work it only cost u some hose. Be VERY CAREFUL how u route the hose.