Suburban Plowboy
Platinum Member
DISCLAIMER: I am not a mechanic, so if you listen to me, you may die or ruin your mower.
I recently bought a Kubota ZD326 diesel mower with 229 hours on the meter. When I arrived to look at it, of course, the meter was frozen, but the mower looks like it has under 1,000 hours on it, so I bought it anyway. The seller knocked a grand off his asking price, which was already pretty good.
Since buying it, I have had some very unpleasant experiences with it. Maybe if I write about them here, it will help others.
I have replaced the hour meter. I replaced the PTO and brake safety switches, none of which turned out to be bad. I disassembled the ignition switch and cleaned it up because I was getting 300k ohms on the "START" setting. I've gone through lots of stuff. I even replaced the stickers on the control panel. I replaced the seat arm rests, and it turns new ones have to have their lousy threads chased with taps in order to receive screws.
Problems:
1. The mower started just fine two or three times at the seller's place, but when I got it home, it balked, and eventually it quit even trying. No cranking.
2. The mower slowed down and almost stopped when I used it. This happened in what seemed to be a random manner.
3. It quit stopping with the key, so I had to pull a lever on the engine to shut it off.
I got some really bad advice about the bogging issue. I was told the controller (ECM) ran the fuel system, so a bad ECM could make the motor slow down and quit. This is not true. In case anyone is interested, the ECM does only three things, and it connects to three relays that make all these things happen:
1. It monitors the lawyer switches and refuses to let you start the mower if they are not in the right positions OR there is a problem with them.
2. It runs the shutdown solenoid for a few seconds when you put the key in the "OFF" position.
3. It runs a horn that goes off when the mower overheats. You don't need this, because there is a temperature gauge on the control panel.
The mower doesn't actually need a computer.
A whole bunch of things can make the mower refuse to crank. I'll list the big offenders, but there are many others.
1. Bad ignition switch.
2. Bad starter relay. The manual's info on testing relays is wrong.
3. Bad safety switch or related wiring.
4. Bad ECM.
In case anyone is interested, the brake safety switch is particularly likely to have problems, and because it's an NC switch (closed when the motor will not start), you can get around it by pulling the receptacle off of it.
I have been through a number of miserable days working on this mower, and I finally used AI and the manuals to write a detailed analysis of the starting system. I went through everything systematically. Now the mower runs like a top.
My ignition switch, relays, and safety switches appear to be fine. It's looking like the ECM is no good, but Kubota doesn't tell its mechanics how to test them, so in order to check it, you have to do a ton of work to eliminate other possibilities and then replace the ECM to see if it helps. If it doesn't help, you wasted over $300 on a dirty ECM you can't return. And you still have no idea what's wrong with your mower.
Kubota won't tell you what's in the ECM, and besides, you can't open it up to fix it.
The good news: you can easily bypass the ECM and run the mower completely normally. You need a jumper wire about 1.5" long with a male spade on each end. You pull off the receptacle on the starter relay and insert the jumper across the black/yellow and black/white wires.
This will render your safety switches inoperable, so while it saves you a lot of time and money, it could also kill you or someone nearby. Choose your priorities. Sloppy yard, or snazzy state-of-the-art prosthetics.
If you do this AND the ECM is no good, you will have to stop the mower manually or come up with your own fuel shutdown circuit, which is not hard for electronics whizzes. You will also have to make sure your temperature gauge works, because your heat alarm will not.
I am thinking of installing a choke cable on the manual shutoff and putting the knob by my seat. I have a design for a shutoff circuit, but I don't see the point in adding something else that is relatively fragile.
A bad ground on the ECM could also cause the mower to refuse to crank and shut down. I have not removed my ground and cleaned it yet because shoving that wire in the relay receptacle was a lot easier, and my yard really needed mowing. I very much doubt the ground is bad, because it looks very nice.
You can rig the safety switches up to work using cheap components like the ones in older tractors. There is no reason for a complicated ECM that will fail and be discontinued long before the mower wears out.
I hate seat switches, but I like the one on this mower because it will not shut the mower down unless the blades are engaged. The mower has a seat belt, though, and in comparison, I think the seat switch is worthless, because if you fall in front of the mower and the switch works immediately, the blades will still be turning when the mower goes over you.
Bottom line, though: make sure your mower is safe to start or dismount before you turn the key or get off, wear your belt, and you should be fine.
The fuel issue has nothing to do with the ECM. There is apparently some goo in the left tank. The mower runs fine on the right tank. I plan to drain the left tank and dispose of the fuel properly (loosely defined), and I have also treated both tanks with Clear-Diesel.
Interesting fact: my L3710 is much more complicated yet has no ECM to die or be discontinued by Kubota. My John Deere 430 also has no ECM. You don't need a computer to make a machine run just fine, complete with safety switches.
While I was working on this, I realized I needed to think about ECM's while I look for a bigger tractor. I am told Kubota didn't use ECM's until the 2013 year. Maybe someone can correct this. I was told the L5030 was the last ECM-free HST mower in the size range I like, so that makes it a serious shopping target.
I was considering a TYM T574 without much in the way of electronics, but they have front axle problems, sometimes the front wheels fall off, and I read that they have inferior bearings in the rear axle, so I am hesitant now.
I recently bought a Kubota ZD326 diesel mower with 229 hours on the meter. When I arrived to look at it, of course, the meter was frozen, but the mower looks like it has under 1,000 hours on it, so I bought it anyway. The seller knocked a grand off his asking price, which was already pretty good.
Since buying it, I have had some very unpleasant experiences with it. Maybe if I write about them here, it will help others.
I have replaced the hour meter. I replaced the PTO and brake safety switches, none of which turned out to be bad. I disassembled the ignition switch and cleaned it up because I was getting 300k ohms on the "START" setting. I've gone through lots of stuff. I even replaced the stickers on the control panel. I replaced the seat arm rests, and it turns new ones have to have their lousy threads chased with taps in order to receive screws.
Problems:
1. The mower started just fine two or three times at the seller's place, but when I got it home, it balked, and eventually it quit even trying. No cranking.
2. The mower slowed down and almost stopped when I used it. This happened in what seemed to be a random manner.
3. It quit stopping with the key, so I had to pull a lever on the engine to shut it off.
I got some really bad advice about the bogging issue. I was told the controller (ECM) ran the fuel system, so a bad ECM could make the motor slow down and quit. This is not true. In case anyone is interested, the ECM does only three things, and it connects to three relays that make all these things happen:
1. It monitors the lawyer switches and refuses to let you start the mower if they are not in the right positions OR there is a problem with them.
2. It runs the shutdown solenoid for a few seconds when you put the key in the "OFF" position.
3. It runs a horn that goes off when the mower overheats. You don't need this, because there is a temperature gauge on the control panel.
The mower doesn't actually need a computer.
A whole bunch of things can make the mower refuse to crank. I'll list the big offenders, but there are many others.
1. Bad ignition switch.
2. Bad starter relay. The manual's info on testing relays is wrong.
3. Bad safety switch or related wiring.
4. Bad ECM.
In case anyone is interested, the brake safety switch is particularly likely to have problems, and because it's an NC switch (closed when the motor will not start), you can get around it by pulling the receptacle off of it.
I have been through a number of miserable days working on this mower, and I finally used AI and the manuals to write a detailed analysis of the starting system. I went through everything systematically. Now the mower runs like a top.
My ignition switch, relays, and safety switches appear to be fine. It's looking like the ECM is no good, but Kubota doesn't tell its mechanics how to test them, so in order to check it, you have to do a ton of work to eliminate other possibilities and then replace the ECM to see if it helps. If it doesn't help, you wasted over $300 on a dirty ECM you can't return. And you still have no idea what's wrong with your mower.
Kubota won't tell you what's in the ECM, and besides, you can't open it up to fix it.
The good news: you can easily bypass the ECM and run the mower completely normally. You need a jumper wire about 1.5" long with a male spade on each end. You pull off the receptacle on the starter relay and insert the jumper across the black/yellow and black/white wires.
This will render your safety switches inoperable, so while it saves you a lot of time and money, it could also kill you or someone nearby. Choose your priorities. Sloppy yard, or snazzy state-of-the-art prosthetics.
If you do this AND the ECM is no good, you will have to stop the mower manually or come up with your own fuel shutdown circuit, which is not hard for electronics whizzes. You will also have to make sure your temperature gauge works, because your heat alarm will not.
I am thinking of installing a choke cable on the manual shutoff and putting the knob by my seat. I have a design for a shutoff circuit, but I don't see the point in adding something else that is relatively fragile.
A bad ground on the ECM could also cause the mower to refuse to crank and shut down. I have not removed my ground and cleaned it yet because shoving that wire in the relay receptacle was a lot easier, and my yard really needed mowing. I very much doubt the ground is bad, because it looks very nice.
You can rig the safety switches up to work using cheap components like the ones in older tractors. There is no reason for a complicated ECM that will fail and be discontinued long before the mower wears out.
I hate seat switches, but I like the one on this mower because it will not shut the mower down unless the blades are engaged. The mower has a seat belt, though, and in comparison, I think the seat switch is worthless, because if you fall in front of the mower and the switch works immediately, the blades will still be turning when the mower goes over you.
Bottom line, though: make sure your mower is safe to start or dismount before you turn the key or get off, wear your belt, and you should be fine.
The fuel issue has nothing to do with the ECM. There is apparently some goo in the left tank. The mower runs fine on the right tank. I plan to drain the left tank and dispose of the fuel properly (loosely defined), and I have also treated both tanks with Clear-Diesel.
Interesting fact: my L3710 is much more complicated yet has no ECM to die or be discontinued by Kubota. My John Deere 430 also has no ECM. You don't need a computer to make a machine run just fine, complete with safety switches.
While I was working on this, I realized I needed to think about ECM's while I look for a bigger tractor. I am told Kubota didn't use ECM's until the 2013 year. Maybe someone can correct this. I was told the L5030 was the last ECM-free HST mower in the size range I like, so that makes it a serious shopping target.
I was considering a TYM T574 without much in the way of electronics, but they have front axle problems, sometimes the front wheels fall off, and I read that they have inferior bearings in the rear axle, so I am hesitant now.
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