Kohler EFI engine swap in Deere LX173 wiring question...

I have installed a new Kohler EZT740-3022, 25 hp fuel injected engine in a Deere LX173. The original engine was a Kohler CV15. Mechanically everything has been modified and the new engine is installed in the tractor, including the ability to close the modified hood.

I have run into the challenge of how to wire the Deere’s 4 pin “W2 Engine Wiring Harness” connector to mate with the new Kohler’s 6 pin connector.

I purchased a matching male connector to the Kohler 6 pin connector to replace the original Deere 4 pin “Engine Wiring Harness” connector. I thought I understood the wiring diagram; I had the Deere white Ignition Module wire pin opposite the Kohler white wire, engine wouldn't start and I realized the Kohler white wire was going to Diagonistic Connector. It seems that 3 of the Deere wires are a simple match to 3 of the Kohler pins to mate together. The big challenge seems to be what to do with the Deere #940 white wire that went to the original single cylinder ignition module.

The Kohler has the following 6 pin wire connector from the engine: [Information from page 36 EFI System in the Service Manual]
#1 pin empty
#2 pin-white wire leads to diagnostic connector
#3 pin- black wire leads to Malfunction Indicator Lamp, MIL (installed MIL in dash on Deere)
#4 pin- red/white wire leads to ignition switch
#5 pin- green wire leads to oil pressure sentry sensor, this engine does not have an oil sentry on it.
#6 pin- dark blue wire leads to starter

The Deere has the following wires: (numbers are from Deere Service Manual wiring layout; the first 4 wires were in the original Deere 4 wire “W2 Engine Wiring Harness” connector that mated to the original Kohler CV15 engine)
1) #205- red wire, key switch
2) #416- yellow/black wire, fuel shut-off for carb solenoid
3) #620- tan wire, engine oil sentry
4) #940- white wire, ignition module

#721- purple/while wire, starter motor (this wire had a separate connector to the original Kohler CV15 engine starter)

It seems that the following 4 wires mate together, the wires have pinned to correspond to the new Kohler engine connector:
Deere # 205, key switch would mate to the Kohler #4 pin to the ignition switch
Deere # 620, engine oil sentry would mate to the Kohler #5 pin to the oil sentry (may add the oil sentry later)
Deere #721, starter motor wire would mate to the Kohler #6 pin to the starter
New wire to mate with from Kohler #3 pin to the MIL, Malfunction Indicator Lamp installed on dash

The question is where should the Deere #940 white wire for the ignition module connect to? I tried the white wires but had no success, that is when I realized the Kohler white wire fed directly to the Diagnostic Connection. Is the Deere #416 fuel shut-off solenoid wire necessary to connect to the new EFI engine or is this now to be clipped and abandoned?

We live on an off-grid remote ranch in S.E. Oregon the closest town that might have a technician that possibly could help is over two hours away, and realistically more than likely almost 4 hours away. If possible, I need to resolve this issue here on the ranch. I greatly appreciate any advice anyone can give me.

This is my favorite series to work on! I work at a Deere dealership and will be happy to help.

I am attaching a wiring schematic.

The area inside the dotted lines is your circuit board attached to the keyswitch.

The white wire seems to be the kill wire for the old ignition coil.
Looks like the safety system used this wire to kill the spark to the engine.
You may need to connect it to your new ignition coils for the engine shut-off and safety system to work correctly.

The solenoid wire is 'hot' when the keyswitch is on, and also works in conjunction with your safety system to shut the fuel flow off to the engine if something bad happens. I would connect this wire to whatever wire will shut down the power to the EFI to stop fuel from getting to the engine as that was it's original purpose on the old engine. An idea would be to have this wire power the fuel pump. That way, it would shut the pump off.

In summary, the white wire grounds the ignition, and the solenoid wire would shut off the fuel supply in order to shut the engine down.

I am leaving the shop for the day (it is 5pm here on the east coast), but will check back in the morning.

Take a look at the schematic and let me know if you have any questions.

Thanks! -Will

Will,
Thank you for your response, your answer makes sense. I will not be able to work on the Deere until Friday. I'll let you know the results. I have the new Kohler Service Manual so the wire identification is the easy part; then it is just figuring the best place to attach into the circuit before the ignition coil and fuel pump.

When the engine died I contacted some re-engine firms and was told due to size restrictions I couldn't put a new engine on this Deere. I was pleased with the life of the old Kohler engine and when I found that this EFI Kohler appeared to fit on the chassis; I made a wood cut-out of the engine base from the spec page drawings to check fit. I decided to go for the swap. It took a fair amount of modification to get the hood to fit. I plan to box the hood sides to protect the side of the engine like the 318 model had. I had read that if I stayed with the Kohler family that the wiring would be an easier retro-fit; so decided to go with the Kohler EFI engine. I knew it would be challenge and it has been.

We live at 5,100' in elevation, which required putting a high-altitude jet in the old carb. I was told the EFI engine would not be a problem at this altitude. I didn't feel the need for the 25 hp engine; Kohler shows a 20 hp EFI but I was informed it wouldn't be available until early next year. We need to get this little Deere working before then.

I was concerned about putting that much power increase on the transaxle. I was told the Peerless 801 was supposed be a fairly robust transaxle and that should be able to handle the increase, no hot rodding the tractor. The transaxle doesn't have any leaks and has never shown any issues. Time will tell. We don't abuse our equipment, use it yes but not abuse it. Even if I should have to replace the transaxle in the future I feel the total cost of keeping the old Deere running would be less than trying to buy an equivalent new tractor. I looked for a possible used replacement but felt a new engine made more economic sense.

MJM48 said:

Will,
Thank you for your response, your answer makes sense. I will not be able to work on the Deere until Friday. I'll let you know the results. I have the new Kohler Service Manual so the wire identifcation is the easy part; then it is just figuring the best place to attach into the circuit before the ignition coil and fuel pump.

When the engine died I contacted some re-engine firms and was told due to size restrictions I couldn't put a new engine on this Deere. I was pleased with the life of the old Kohler engine and when I found that this EFI Kohler appeared to fit on the chasis; I made a wood cut-out of the engine base from the spec page drawings to check fit. I decided to go for the swap. It took a fair amount of modification to get the hood to fit. I plan to box the hood sides to protect the side of the engine like the 318 model had. I had read that if I stayed with the Kohler family that the wiring would be an easier retro-fit; so decided to go with the Kohler EFI engine. I knew it would be challenge and it has been.

We live at 5,100' in elevation, which required putting a high altitude jet in the old carb. I was told the EFI engine would not be a problem at this altitude. I didn't feel the need for the 25 hp engine; Kohler shows a 20 hp EFI but I was informed it wouldn't be available until early next year. We need to get this little Deere working before then.

I was concerned about putting that much power increase on the transaxle. I was told the Peerless 801 was supposed be a fairly robust transaxle and that should be able to handle the increase, no hot rodding the tractor. The transaxle doesn't have any leaks and has never shown any issues. Time will tell. We don't abuse our equipment, use it yes but not abuse it. Even if I should have to replace the transaxle in the future I feel the total cost of keeping the old Deere running would be less than trying to buy an equivalent new tractor. I looked for a possible used replacement but felt a new engine made more economic sense.

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Your transmission should be ok with that engine. It's big brother, the LX188, had a 17hp engine in it so you should be fine. Let me know how you make out. I usually check my messages about 8 or 9AM eastern time.

Question: I'm not sure where or how I should connect the Deere wires. I've attached the new engine wiring diagram and highlighted the ignition coils and fuel pump. I'm not well versed in electrical engineering so I'm not sure if I can just use a clamp on connector to the red/black wires ("B" wire) just prior to the ingition coils and fuel pump wires or if I need to cut those power wires and somehow route the circuit through the Deere wires.

I may be trying to over think this. At first I thought I could just attach a clamp connector from the Deere wires at the coils and fuel pump but then I started seconding guessing myself and thought, "no that wouldn't break the circuit and act as a kill/shut-off." I do appreciate your perspective and help.
MJM

MJM48 said:

Question: I'm not sure where or how I should connect the Deere wires. I've attached the new engine wiring diagram and highlighted the ignition coils and fuel pump. I'm not well versed in electrical engineering so I'm not sure if I can just use a clamp on connector to the red/black wires ("B" wire) just prior to the ingition coils and fuel pump wires or if I need to cut those power wires and somehow route the circuit through the Deere wires.

I may be trying to over think this. At first I thought I could just attach a clamp connector from the Deere wires at the coils and fuel pump but then I started seconding guessing myself and thought, "no that wouldn't break the circuit and act as a kill/shut-off." I do appreciate your perspective and help.
MJM

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I had some time to check messages this afternoon. Thanks for the diagram. Let me put that beside the original schematic and figure this out. We can make this work!

At the risk of clouding the issue here I have a few questions.

I was under the impression the "igniter" used in the old engines performed the functions of ignition dwell (i.e. how long the coil stayed on) electronically (as opposed to even older setups that used mechanical points for that). Pull that wire and the coil can't fire, all of which is irrelevant to any ignition system that handles dwell some other way, such as later ignition coils with internal dwell control, and of course EFI systems.

I'd expect an EFI engine to stop once power is cut to its computer, no? Other than keyswitch wires for run and start, what else would it need? We're assuming the engine is still grounded to frame via its block, an additional ground cable, and that the original Deere harness is still also grounded to frame or engine so that the ignition switch retains its ground, yeah?

And the big question, have you attempted to fire the engine yet?

deckeda said:

At the risk of clouding the issue here I have a few questions.

I was under the impression the "igniter" used in the old engines performed the functions of ignition dwell (i.e. how long the coil stayed on) electronically (as opposed to even older setups that used mechanical points for that). Pull that wire and the coil can't fire, all of which is irrelevant to any ignition system that handles dwell some other way, such as later ignition coils with internal dwell control, and of course EFI systems.

I'd expect an EFI engine to stop once power is cut to its computer, no? Other than keyswitch wires for run and start, what else would it need? We're assuming the engine is still grounded to frame via its block, an additional ground cable, and that the original Deere harness is still also grounded to frame or engine so that the ignition switch retains its ground, yeah?

And the big question, have you attempted to fire the engine yet?

Click to expand...

Deckeda, that is exactly what I was thinking as well. I am checking the original tractor harness and making the sure the power wire for the original carb functions with the safety system, and it looks like it does. I dont want to wire the machine straight from the keyswitch as that would compromise the safety system.

MJM, if you could do a few tests with a digital volt meter or test light, that would be great. Here is a list:

1. With keyswitch on, transmission in neutral, PTO switch off, parking brake locked, the carb wire should have voltage. This similates the starting conditions.
2. With keyswitch on, transmission in any gear, PTO switch on, parking brake released, and operator on seat, the wire should have voltage. This similates the normal mowing conditions.
3. With same settings as #2, except operator off seat, the wire should NOT have voltage. Verify that the voltage turns off when the operator leaves the seat. This similates someone falling off the machine while mowing. If the voltage turns off when you come off the seat, we should be good to go.

Will1988 said:

Deckeda, that is exactly what I was thinking as well. I am checking the original tractor harness and making the sure the power wire for the original carb functions with the safety system, and it looks like it does. I dont want to wire the machine straight from the keyswitch as that would compromise the safety system.

MJM, if you could do a few tests with a digital volt meter or test light, that would be great. Here is a list:

1. With keyswitch on, transmission in neutral, PTO switch off, parking brake locked, the carb wire should have voltage. This similates the starting conditions.
2. With keyswitch on, transmission in any gear, PTO switch on, parking brake released, and operator on seat, the wire should have voltage. This similates the normal mowing conditions.
3. With same settings as #2, except operator off seat, the wire should NOT have voltage. Verify that the voltage turns off when the operator leaves the seat. This similates someone falling off the machine while mowing. If the voltage turns off when you come off the seat, we should be good to go.

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Will,
I used a test light and yes it followed the 3 steps you listed above. At the risk of jumping ahead of your thinking as I studied the wiring diagram for the Kohler EFI with your insight I have the following 4 questions.
1. Should the Deere white wire #940 (which is part of the fuel shut-off system) be wired to the Kohler 6 pin connector in the #4 pin location. As I read the diagram it appears this Kohler red/black wire powers the ignition coils and the fuel pump.
2. Should the Deere yellow/black wire #416 (carb solenoid fuel shut-off ) be tied into the same Kohler pin as above (#4 in the 6 pin connector that powers ignition coils and fuel pump) this would in affect be the fuel pump shut-off.
3. Where should the Deere red wire #205 go? This #205 red wire was part of the original 4 pin connector to the old CV15 engine. Based on my limited understanding from your first post this appears to also be part of the fuel shut-off system. If questions 1,2, and 3 are correct this would make 3 Deere wires, (white #940; yellow/black #416 and red 205 all connected to the Kohler #4 pin in the 6 pin connector.
4. The Kohler #2 pin, white wire which connects to the Diagnostic Connector is shown connecting into the #14 pin in the Grey Connector on the ECU (2 pages before the wiring diagram I attached). The number 14 pin is titled, "Safety Switch Ground." Should I attach a ground in the Deere 6 pin connector to complete the Kohler 6 pin connector wiring?
I hope these 4 questions haven't muddied the water.

I had some time today but will not be able to do further tests/work until Friday. Thank you again so much for your time and insight.
Mike

deckeda said:

At the risk of clouding the issue here I have a few questions.

I was under the impression the "igniter" used in the old engines performed the functions of ignition dwell (i.e. how long the coil stayed on) electronically (as opposed to even older setups that used mechanical points for that). Pull that wire and the coil can't fire, all of which is irrelevant to any ignition system that handles dwell some other way, such as later ignition coils with internal dwell control, and of course EFI systems.

I'd expect an EFI engine to stop once power is cut to its computer, no? Other than keyswitch wires for run and start, what else would it need? We're assuming the engine is still grounded to frame via its block, an additional ground cable, and that the original Deere harness is still also grounded to frame or engine so that the ignition switch retains its ground, yeah?

And the big question, have you attempted to fire the engine yet?

Click to expand...

Hi deckeda,

Didn't mean to ignore your question, yes I tried to fire the engine and had nothing that is when I began looking on-line for answers. I wrote Kohler, didn't get a response, yet, and then I found this forum and submitted my original post. Will has been great in helping me to understand more of the original Deere wiring and how that relates to the new Kohler wiring. I do so much appreciate the time and thoughts from both of you.
Mike