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Discussion Starter #1
I have a 1989 318 with a Kohler engine. It has a history of not starting (and once dying) due to loose wires at the ignition switch. This time it has the same symptoms but I have checked the wiring at the ignition switch and even replaced the switch to no avail. Here is what I know:

1. The starter won't even click.
2. My voltmeter indicates that power is getting to the starter solenoid.
3. When I use a screwdriver or jumper wire to connect the two terminals on the starter solenoid, the starter whirls but the tractor doesn't start.
4. When the hot red ignition wire (Wire B, I believe) touches one of the purple ignition wires, the tractor tries to start.

Does anyone have insights on next steps? I am learning but am new to this, so any assistance would be greatly appreciated! Thanks!
 

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:wgtt:

Do you have the TM1590 manual? The 1989 318 tractors came from the factory with the Onan P218 twin engine -- has your tractor been re-powered? If it is indeed a repower, then the wiring may be far different from what a stock tractor should have, but in any event a properly done re-power should still have the safety interlock switches that prevent the starter from cranking the engine unless the ground speed lever is in the Neutral/Stop slot and the PTO switches are off. Here is the wiring in that area for a stock Onan powered tractor:
318 Starting circuit.JPG

None of the ignition wires are purple, but the power through the safety switches to the solenoid are purple wires -- from the solenoid itself to the S1 terminal of the key switch is wire #700, fro the key switch terminal S2 to the brake switch is wire #710, etc. Tractors below SN 600,304 do not have a brake switch, and the #710 wire goes directly to the neutral switch in place of the #715 purple/white wire. This change occurred DURING the 1989 model year, so check your serial number.

Once the starter cranks the engine the engine should start if the proper ignition conditions are met. Here is the excerpt of the ignition wiring for the Onan (again -- please let us know if your tractor really has a Kohler engine and some information on which one and how it was wired into the factory harness...)
ignition diagram 318.JPG

Often a bad F2 fuse or a failed seat switch or harness in the seat switch area interferes with an engine getting ignition. Let us know what you find and we can continue trouble shooting.

Chuck
 

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Discussion Starter #3
More Information

Thank you very much, Chuck. I really appreciate your help. Here is some additional information:

1. The Product ID No. is M00318x433807, which appears to be below 600,304. (The 710 wire goes directly to the neutral switch, which confirms that.) The original engine serial no. was E873215288

2. The prior owner repowered the engine in 2004 with a Kohler Command engine (Model CH22S, I believe though not for certain).

3. Here is what I have at the ignition switch:

Prong A is off to the side and then there are 5 prongs arranged like this (I am using the designations I found online):

S2
B S1
| |

Prong A terminates a pink and red wire. The pink wire runs to a yellow wire that goes through a yellow fuse and then runs into a pink wire. The red wire goes through a black and white cylinder. The connection on these wires is hot when the key is in the run position. When I turn the key to the run position, the oil and batter lights activate on the dash, which appears to be controlled by the wire at prong A.

S2 connects to a single purple wire.

B connects to a single red wire. This wire is always hot, even when the key is in the off position.

S1 connects to 1 purple wire and 1 purple/black wire. The purple wire goes directly to the neutral switch.

It is difficult for me to tell where most of the wires end up going because they are all bound together with wrap. I can certainly remove that if needed.

As I mentioned before, when hot wire B hits the S2 connection, the tractor tries to start.

Thank you again!

Trent

:wgtt:

Do you have the TM1590 manual? The 1989 318 tractors came from the factory with the Onan P218 twin engine -- has your tractor been re-powered? If it is indeed a repower, then the wiring may be far different from what a stock tractor should have, but in any event a properly done re-power should still have the safety interlock switches that prevent the starter from cranking the engine unless the ground speed lever is in the Neutral/Stop slot and the PTO switches are off. Here is the wiring in that area for a stock Onan powered tractor:
View attachment 49127

None of the ignition wires are purple, but the power through the safety switches to the solenoid are purple wires -- from the solenoid itself to the S1 terminal of the key switch is wire #700, fro the key switch terminal S2 to the brake switch is wire #710, etc. Tractors below SN 600,304 do not have a brake switch, and the #710 wire goes directly to the neutral switch in place of the #715 purple/white wire. This change occurred DURING the 1989 model year, so check your serial number.

Once the starter cranks the engine the engine should start if the proper ignition conditions are met. Here is the excerpt of the ignition wiring for the Onan (again -- please let us know if your tractor really has a Kohler engine and some information on which one and how it was wired into the factory harness...)
View attachment 49128

Often a bad F2 fuse or a failed seat switch or harness in the seat switch area interferes with an engine getting ignition. Let us know what you find and we can continue trouble shooting.

Chuck
 

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Trent,

Excellent additional information -- thank you! The serial number of your tractor indicates that it is a 1987 year model, which ran from serial numbers 420,001 through 475,000. Further, the serial number of the original Onan engine has a date code prefix that shows it was manufactured in May of 1987. You may wish to take the serial number of the tractor into consideration when ordering parts as there were many running changes during the long production of the 318 that did not occur on year model boundaries. Most likely the Kohler in your tractor now is the 22 HP Command engine...there were even some commercially available "kits" to do this swap.

I am unfamiliar with the ignition changes when re-powering with a Kohler twin but a search of this site should give you some reading to start with. I do recall that the Kohler needs an engine harness wire grounded to kill the ignition whereas the Onan just needed voltage removed to do the same function. Due to this difference, the key switch on your tractor may have been changed to one a different internal configuration when the engine was swapped, or an external relay may have been added. Replacing the key switch with a correct one for the Onan engine may in fact be at the root of all your present symptoms. Other wiring on the tractor may also have been altered by the prior owner that did the swap -- sometimes those are done with care and consideration of the original safety system's intent, but sometimes they are pretty badly hacked. You will have to trace it all out to know for sure (or find the instructions of the engine swap kit if one were used...)

It appears that some kits use a pre-wired harness with a relay like you see here Kohler John Deere 318 Kit but your tractor may have been done without a kit by a creative (or just doggedly determined) prior owner.

Maybe a member here or on WFM would have some more specific familiarity with such a repower, and perhaps they can chime in to help us...

Chuck
 

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Trent,

I found this on-line to show how different a key switch for a Kohler would be from the original key switch used with the Onan. The Kohler engine does indeed need to have the engine harness 'kill' wire grounded to stop the engine. Perhaps the switch you took out recently was substantially different than the one you just put in???
Kohler ignition switch.jpg

...maybe this will help a bit.

Chuck
 

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Discussion Starter #6
Thanks, Chuck. That is definitely helpful. The wiring at the ignition switch is definitely the original Onan wiring scheme, not the Kohler repowered scheme. A couple of more comments:

1. I do not get any volts at the spade terminal on the solenoid where the wires comes to it from the relay.

2. From what I have read online, the "B" prong on the switch is in the second row on the side closest to the A prong. That is how my machine has been wired, with the hot red wire (#200) coming to it. I noticed on the ignition switches, however, that there is a B stamped on the prong beside that prong, on the side away from the A prong. I tried switching the hot red wire with the purple/purple-black wire so that the hot red wire was on the prong that has B stamped on it (on the side away from the A prong). The machine actually started but then died as soon as I let the choke up. I don't think that is right, but I was surprised that it actually started.

3. The tractor is a double PTO.

Any thoughts?
 

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Trent,

Here is the contact placement on the switch as used in the stock Onan harness, and the truth table of what is connected where at each position of rotation:

Key switch testing.JPG

Perhaps this document might give further clues -- wish someone that has made this engine transplant would chime in here...this is all I have found from my distant past musings on the WFM site...

Down and dirty wiring connections for a 318 Kohler

Chuck
 

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Trent,

Here is the contact placement on the switch as used in the stock Onan harness, and the truth table of what is connected where at each position of rotation:

View attachment 49218

Perhaps this document might give further clues -- wish someone that has made this engine transplant would chime in here...this is all I have found from my distant past musings on the WFM site...

Down and dirty wiring connections for a 318 Kohler

Chuck
Hi Chuck ! ….. After a bunch of positive coaxing from Terry (T-Mo) LOL …. I meandered over to this sister site of WFM ….

After the Help you gave me Last year with my 318 - Kohler repower wiring issues … I wound up using the Original ignition switch from my Donor Kohler Engine …. a CH22S (spec # 66501)

I found it way easier with NO major Hacking into the 318 system …. BUT there were a few alterations to the way things worked ….. in the end it Works like a Million dollar Champ !!! ….. have after today logged close to 150hrs since the transplant …..

I am as we converse, looking back into my wiring what I did to my system ….. I will Try and see if I can make sense of what was described above …. PS…. The coloured pic you showed above was the Pic that JLang posted when he repowered his 420, and Is a Kohler type switch pattern (the Black wire grounding post is the give away) …. It helped a lot !!!

Cheers … GK
 
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