Scag / Kohler engine has me stumped

[Heavy Metal Doctor]

What happens if you pull the trigger wire going to the starter solenoid while leaving the key in start?

Aaron Z

Yeah, I think a jumper wire test is in order....

If I'm understanding all of the posts correctly, it sounds like the engine fires right up normally in "start" mode, but then shuts off immediately when you release the keyswitch to "run" mode.....That sound to me like you do not have the "run" circuit energized at the engine and it is only firing off the "start" juice.....I would hot-wire the "run" circuit at the engine -- find the to connection for power going to it and put a jumper to it right from the battery. Then "run" will be live all the time and eliminate the possibilty of a cut wire / bad switch. If this test proves the engine will run, then you will probably find (since it sounds like you put in a new keyswitch allready) that you ran over a stick or something that went up under the machine and damaged / cut the "run" circuit wire between the keyswitch and the engine somewhere.

 

[Gator6x4]

I think the SAM or electronic module is bad. It takes a special tool to test the SAM. Go to section 8 of this service manual for your engine and review the test procedure. http://www.kohlerengines.com/onlinecatalog/pdf/SM_CH18_CH750_1_11.pdf. Your Dealer Service Department should have one of the testers. If not, try another repair source. Paying someone to test the SAM would be better than blindly buying one.

 

[aloha]

Yeah, I think a jumper wire test is in order....

If I'm understanding all of the posts correctly, it sounds like the engine fires right up normally in "start" mode, but then shuts off immediately when you release the keyswitch to "run" mode.....That sound to me like you do not have the "run" circuit energized at the engine and it is only firing off the "start" juice.....I would hot-wire the "run" circuit at the engine -- find the to connection for power going to it and put a jumper to it right from the battery. Then "run" will be live all the time and eliminate the possibilty of a cut wire / bad switch. If this test proves the engine will run, then you will probably find (since it sounds like you put in a new keyswitch allready) that you ran over a stick or something that went up under the machine and damaged / cut the "run" circuit wire between the keyswitch and the engine somewhere.

As suggested I have done a jumper wire test putting 12v to the connector that feeds the ignition components, thus bypassing the switch and all circuits on the Scag side of the connector. The engine runs so long as I keep power on that. I think this narrows down the problem, and I'm going to jury rig it with a jumper to get some desperately needed mowing done. But the fix still eludes me.

The wires on the Scag side of the connector are all well-protected and there is no visible damage. I have to suspect the problem is in the Scag-side electronic module, part # 483029, which interconnects the ignition switch, safety switches, diode and relay, but really don't want to spend over $100 for a new one unless I'm sure it's bad. I have been unable to find an online service manual for the Turf Tiger. Anyone have any thoughts on how to test the electronic module?

 

[aloha]

Oh, man, do I ever feel foolish, but I have learned something: Never trust a visual inspection to determine that a fuse is good.

The first thing I had checked when the mower stopped was the fuses. They both looked good. After having done the jumper wire test I put a multimeter on the fuse for the ignition circuit. No current was getting through it. It still looks good, but I replaced the fuse and the mower now runs.

So, a visual inspection may tell you that a fuse is blown, but don't trust it to determine that a fuse is good.

I sincerely thank everyone who offered up comments and suggestions.

A new problem has surfaced, but hopefully I can sort it out myself. Again, thank you.

 

[TRUBBLESHOETEN]

I have a 6 year old Scag Turf Tiger Kohler 27 engine. It has two 20a spade fuses. It will definitely start and stay running as long as I keep it in the "cranking" position. Only thing is, the starter is being kept engaged. So I replaces the ign/starter switch. Nope.... same problem. I am noticing that either or the other fuse blows after replacing one or the other. I then disconnected "every" safety switch, ammeter, relay, starter and connectors. The only thing that makes any sense at this point, after pugging and connecting each piece one at a time, is the relay!! That is my next step tomorrow. If not the relay... down it will go to my Scag dealer. He's a good guy and won't hurt me $$$ !!!

 

[aloha]

Trubbleshoeten - Before you take to your dealer and spend money . . . What I finally discovered was that the electric PTO clutch had failed and was shorting out, and that was blowing fuses. Your symptoms sound the same as mine, and I went through all the steps (mis-steps?) you describe. I replaced the clutch and have had no problems since. Does yours blow the fuses after you pull the PTO switch, or before? If it is after, that indicates the problem is after that switch. If you have an Ogura clutch, look at http://www.ganos.com/electricclutchadjustment.pdf for test procedures.

 

[TRUBBLESHOETEN]

aloa Thank you. I will check out the clutch tomorrow (Saturday). The following is exactly as it occurred. My Scag Turf Tiger has been in my garage having its deck replaced. While I have been assembling the new deck with some of the parts off the old deck I have been starting the engine at least twice a week for five minutes. Just recently I went to start it and the starter just "clicked" away with that rapid sound it makes when the battery is weak. I checked the battery> weak>disconnected it>trickle-charged it> re-connected it and then the starter didn't even "click". Being a 6 year old battery, it was well passed its time. Installed a new battery and nothing. Checked fuses and one was blown. Installed new fuse and out blew the other, then the other... back and forth. Being that I hadn't even touched the PTO I can't imagine the problem being the clutch. After I re-install the deck tomorrow with the drive shafts hooked up, I'll check out the clutch. Seriously though, I am a firm believer at this point that it's the electronic mod ($90) or the relay ($13)... or both!


thanks trubbleshoeten

 

[aloha]

Trubbleshoeten - Your additional details sound different from my experience, so I agree that my fix probably will not be your solution. Maybe someone else has an idea. You might also want to check the repair forum at lawnsite.com for ideas. There is nothing quite as frustrating as an electrical problem.

 

[TRUBBLESHOETEN]

Trubbleshoeten - Your additional details sound different from my experience, so I agree that my fix probably will not be your solution. Maybe someone else has an idea. You might also want to check the repair forum at lawnsite.com for ideas. There is nothing quite as frustrating as an electrical problem.

I am going back to working on putting it back together tomorrow.... I have been involved with a different project since just before Mother's day. I don't recall if I have informed you; but, after another discussion with my local Scag dealer, he determined that my problem would be with my stator. Sure enough, 1 hour later> magnets were all off the flywheel and clinging to my "damaged" stator. SO... new voltage regulator, flywheel and stator. Now to re-assemble it all and get back to some 5 acres of seriously need mowing! Again, thank you for your help and, please, spread the word about my problem and the fix. take care.

 

[TRUBBLESHOETEN]

I am going back to working on putting it back together tomorrow.... I have been involved with a different project since just before Mother's day. I don't recall if I have informed you; but, after another discussion with my local Scag dealer, he determined that my problem would be with my stator. Sure enough, 1 hour later> magnets were all off the flywheel and clinging to my "damaged" stator. SO... new voltage regulator, flywheel and stator. Now to re-assemble it all and get back to some 5 acres of seriously need mowing! Again, thank you for your help and, please, spread the word about my problem and the fix. take care.

ME AGAIN WITH AN UPDATE: So, 5/21/13> new stator, flywheel, and voltage regulator> all installed. Started right up... 2 minutes into mowing and bamm: dead again. Replaced fuse. Another 5 minutes... again, DEAD. My hands went up in the air and I proclaimed: "I'm done... so done"! Now it's down at the shop. Still my headache, but now it's being shared. Hey, what are friends for ('cept, this headache comes with an invoice.... soon to be "a-hurt'n". Hey, I'll let u guys now the results... hoping to save you a headache. (hey, what are friends for!) Did I say that already?

 

[aloha]

Well, that is unfortunate. Keep us posted. There's nothing quite as much fun as an electrical problem.

 

[TRUBBLESHOETEN]

Well, that is unfortunate. Keep us posted. There's nothing quite as much fun as an electrical problem.

TO ALOHA: Just thought I'd give it some time to prove itself. Anyway, after all the work of the ign switch, module, relay, flywheel, stator, voltage regulator and battery and after it crapping out with the same problem that it had before all the work (and by-the-way most of the electrical parts that were replaced all eventually checked out to be no-good; except for the ign. switch). off it went to the dealer.... where, after replacing the fuse, and after checking all my work the mower did not exhibit one bit of trouble and worked flawlessly for them. They could't find one thing wrong with any of my workmanship! So happy I am art g

 

[TRUBBLESHOETEN]

B U T S T I L L B E W I L D E R E D!!!

 

[Spindles187]

So just been searching online and have same issue with my 2013 Scag Tiger Cat.
It starts when in the start position, but shuts off once you release it from start to ON position.
Bought a new ignition switch and not the problem, changed the fuses hoping that it work work then, but nope still same issue.
Not sure if maybe it is the electronic module.

Thanks

 

[My Hoe]

I didn't read the whole thread, but from my automotive experience, I've read that classic cars ('60's? '70's?) had a "step down circuit" (my words--can't remember the term) that lowered the 12v going into the coil, when CRANKING, to something like 6-7v, for running--I think to prevent overheating the coil.

I'm wondering if modern lawn equip. could still be using 40 year-old technology in this regard, but instead of your "running voltage" stepping down to a less-than-12v value, it's just going away.

Having said that, I believe I read that you replaced the ignition switch, which would seem to eliminate the above, as a possibility, EXCEPT that I don't know how that "step-down" in voltage was accomplished. IOW, maybe it was done somewhere other than the ignition switch?

You could try googling this issue, in the automotive area, and see how those guys diagnose and fix problems with this design, if you could find such a discussion. (I read about it in a Hemmings publication, but I don't know if you can read those, online, w/o a subscription. But I'm sure there are other articles out there).

Good luck!

 

[CCWKen]

Actually, it was the other way around. FULL voltage was applied to the coil during Starting. A reduced voltage was used in Run position. This was accomplished by a physical resister (mostly Chrysler) or resistance wire (Chevy, Ford) in the ignition circuit. In the Start position of the switch, this resistance circuit was bypassed since cranking voltage of the battery was already reduced by the starter draw.

Added:
Perhaps you have it right. After re-reading your statements several times, I'm still confused.

The resistance circuit was employed only in the Run position of the switch. The resistance circuit was NOT in the switch itself.

 

[My Hoe]

Actually, it was the other way around. FULL voltage was applied to the coil during Starting. A reduced voltage was used in Run position. This was accomplished by a physical resister (mostly Chrysler) or resistance wire (Chevy, Ford) in the ignition circuit. In the Start position of the switch, this resistance circuit was bypassed since cranking voltage of the battery was already reduced by the starter draw.

Added:
Perhaps you have it right. After re-reading your statements several times, I'm still confused.

The resistance circuit was employed only in the Run position of the switch. The resistance circuit was NOT in the switch itself.

No, you're right--I had it HALF-right.

I should have stated:

"I've read that classic cars ('60's? '70's?) had a "step down circuit" (my words--can't remember the term) that lowered the 12v going into the coil, when RUNNING (not "CRANKING", as I originally said--no wonder you're confused! LOL) to something like 6-7v, for running--I think to prevent overheating the coil."

But since you've reminded me this "step-down" was accomplished OUTSIDE the keyswitch (and KUDO's for your brand-specific knowledge!), IF that same idea is being used in the OP's Scag, and IF that "RUN" cirucuit is malfunctioning, conceivably, that could explain the OP's symptoms, right?

And thanks for the refresher--I obviously needed it!

My Hoe

 

[murphy1244]

No, you're right--I had it HALF-right.

I should have stated:



But since you've reminded me this "step-down" was accomplished OUTSIDE the keyswitch (and KUDO's for your brand-specific knowledge!), IF that same idea is being used in the OP's Scag, and IF that "RUN" cirucuit is malfunctioning, conceivably, that could explain the OP's symptoms, right?

And thanks for the refresher--I obviously needed it!

My Hoe

GM used a nickel wire for the run circuit and Dodge used the infamous ballast resister.

 

[My Hoe]

GM used a nickel wire for the run circuit and Dodge used the infamous ballast resister.

Cool--I didn't know that--now I know where to get some real nickel (for whatever use it might serve--experimenting while brazing, perhaps?) the next time I get to the junkyard. Amazing what you can learn here! :thumbsup:

 

[murphy1244]

Cool--I didn't know that--now I know where to get some real nickel (for whatever use it might serve--experimenting while brazing, perhaps?) the next time I get to the junkyard. Amazing what you can learn here! :thumbsup:

That was on the old points cars and was dropped when they started using the HEI