Starting Trouble

Justin Charles

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Equipment
2008 Kubota MX5000SU
Feb 22, 2021
9
0
1
Ocala, Florida
My 2008 MX5000SU will crank but not start unless I remove the fuel shutoff solenoid. If the solenoid is in place the it will only crank and blow a 10A fuse every time. I've tested the 2 pin solenoid by connecting it directly to the battery and nothing happens - the thin plunger doesn't move. I've also tested the wiring harness plug that goes to the solenoid and don't get a reading there either. Anyone have any ideas as to what could be wrong ? I ordered a new solenoid for it but am concerned about ruining it if the problem lies elsewhere. Thanks in advance for any and all suggestions !!!
 

Roadworthy

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Find a wiring diagram for your tractor. It is possible the solenoid's electrical return path is through ground. One of your terminals may get an activation voltage from the start position and a slightly lower run voltage from the key in the run position. If your solenoid has two coils like that it's possible one has shorted to ground blowing your fuse. If that's the case your new solenoid should cause no further problem.
 
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PoTreeBoy

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There's a WSM for the MX5000 on www.kubotabooks.com. However, the schematic doesn't show a fuel shutoff solenoid and the engine section shows a manual shutdown. There must have been a change during production or perhaps the -SU is different.
I think the solenoid will fix your issue since it starts with the solenoid removed. You should have +12 volts on at least one of the connector pins with the key on (and good fuses).
 
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Justin Charles

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2008 Kubota MX5000SU
Feb 22, 2021
9
0
1
Ocala, Florida
Find a wiring diagram for your tractor. It is possible the solenoid's electrical return path is through ground. One of your terminals may get an activation voltage from the start position and a slightly lower run voltage from the key in the run position. If your solenoid has two coils like that it's possible one has shorted to ground blowing your fuse. If that's the case your new solenoid should cause no further problem.
Thanks for your reply. I should have the new solenoid in a few days. Hope that does it! Kubota dealer wanted $150 for the part. I got it fo $55 incl shipping! Exact same part.
 

Dave_eng

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M7040, Nuffield 465
Oct 6, 2012
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I have attached the wiring diagram I believe is for your tractor. It appears to have an OPC system for Operator Protection System..

I also marked up a portion of the wiring diagram involving the Stop Solenoid.

The solenoid has two internal coils but that is misleading as the wiring for both internal coils is tied together. The solenoid is grounded through the body. Your test of applying power might not reflect the ground connection though the solenoid body.

Forum MX5000 opc.jpg


If your tractor has the OPC system then, when some safety switch is out of its normal position, the timer is sending a few seconds of power to the engine stop solenoid via the relay thus stopping the engine.

You comment that the engine starts with the stop solenoid removed. I suggest before you do the replacement you try unplugging the electrical connection. If a relay or timer has failed it could be powering the solenoid continuously preventing starting.

Dave
 

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Justin Charles

New member

Equipment
2008 Kubota MX5000SU
Feb 22, 2021
9
0
1
Ocala, Florida
I have attached the wiring diagram I believe is for your tractor. It appears to have an OPC system for Operator Protection System..

I also marked up a portion of the wiring diagram involving the Stop Solenoid.

The solenoid has two internal coils but that is misleading as the wiring for both internal coils is tied together. The solenoid is grounded through the body. Your test of applying power might not reflect the ground connection though the solenoid body.

View attachment 55353

If your tractor has the OPC system then, when some safety switch is out of its normal position, the timer is sending a few seconds of power to the engine stop solenoid via the relay thus stopping the engine.

You comment that the engine starts with the stop solenoid removed. I suggest before you do the replacement you try unplugging the electrical connection. If a relay or timer has failed it could be powering the solenoid continuously preventing starting.

Dave
Thanks Dave - That’s very helpful! Could be relay if not solenoid.
 

Henro

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B2910, BX2200, KX41-2V mini Ex.
May 24, 2019
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My 2008 MX5000SU will crank but not start unless I remove the fuel shutoff solenoid. If the solenoid is in place the it will only crank and blow a 10A fuse every time. I've tested the 2 pin solenoid by connecting it directly to the battery and nothing happens - the thin plunger doesn't move. I've also tested the wiring harness plug that goes to the solenoid and don't get a reading there either. Anyone have any ideas as to what could be wrong ? I ordered a new solenoid for it but am concerned about ruining it if the problem lies elsewhere. Thanks in advance for any and all suggestions !!!
In addition to what Dave said, you should be able to physically move the solenoid armature in and out by pushing (or pulling) on it. It will have a spring holding it in one position. You move it, and it returns to its natural position. If it does not move it must be frozen in position, which is abnormal.

Since the tractor starts with the solenoid removed, it sounds like the armature is stuck in the extend position, and that the extend position is the fuel cut off position.

If You are unable to relatively easily move the solenoid armature, the solenoid is likely bad. If you have a multimeter, measure the resistance between each wire and the metal solenoid case. Should be the same, and likely more than a couple ohms each (just guessing the value). A very low reading would indicate why the 10 amp fuse is blowing.
 

PoTreeBoy

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Please ignore my previous post.

But, according to Dave_Eng's schematic, a bad solenoid wouldn't be blowing a 10 amp fuse. It's only protected by the main fuse/fusible link.
Does that fuse blow even without the solenoid connected? If so, I suspect a wiring short in the interlock circuit.
You can check the solenoid by grounding the case and applying +12 volts to both pins.
Since you have the shutoff timer, you should see 12 volts at the solenoid connector for about 5 seconds when you turn the key from on to off. Any other time it should be 0.
 

retired farmer

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tractor, loader, cutter, blade
May 25, 2020
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sheridan
Just curious, what is wrong with installing a push pull cable shut off for fuel like on the older tractors?
I am not a fan of all the electronic gizzmos.
 

Dave_eng

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Oct 6, 2012
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Williamstown Ontario Canada
Just curious, what is wrong with installing a push pull cable shut off for fuel like on the older tractors?
I am not a fan of all the electronic gizzmos.
The fundamental principle aspect of North American safety systems is stopping the engine automatically when operating conditions are deemed unsafe or to prevent staring under similar unsafe conditions.

On old tractors like the Nuffield 465, all that the designers were concerned with was preventing you from staring in gear. If youfell off and got run over by your own machine that was just Darwin's principles at work. Same thing if you got off the tractor with the pto still engaged and got too close to the pto shaft or a running implement.

As tractor owners who did not grow up on a tractor began buying and using them and getting hurt, the safety design philosophy changed.

Now electronic brains decide if conditions are right to allow the engine to start, to keep running if started and what to do if you get off the seat with the pto engaged.

You cannot buy a new North American machine without the electronic systems. Further, the latest engine operation is completely electronically controlled for reasons of emission control.

Dave
 

Henro

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B2910, BX2200, KX41-2V mini Ex.
May 24, 2019
1,252
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Please ignore my previous post.

But, according to Dave_Eng's schematic, a bad solenoid wouldn't be blowing a 10 amp fuse. It's only protected by the main fuse/fusible link.
Does that fuse blow even without the solenoid connected? If so, I suspect a wiring short in the interlock circuit.
You can check the solenoid by grounding the case and applying +12 volts to both pins.
Since you have the shutoff timer, you should see 12 volts at the solenoid connector for about 5 seconds when you turn the key from on to off. Any other time it should be 0.
I could not view Dave's pdf file on my ipad for some reason...

You are correct that according to the schematic, the 40 amp fuse does feed the fuel cut off solenoid directly. But doesn't this seem a bit strange? I have seen mistakes on schematics before.

I do know the fuel shutoff solenoid on my BX2200, of course a different tractor and this may be irrelevant, but it is fed by a 5 amp fuse. Since the OP has one known problem, and the 10 amp fuse blows when he tries to start the tractor with everything connected, this would seem to indicate there is a relationship between the fuse blowing and the issue that keeps the tractor from starting... It takes very little effort to move whatever is within the injector pump to cut the fuel off. Just seems like needing to supply high amperage to make this happen would not be required.
 

PoTreeBoy

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I could not view Dave's pdf file on my ipad for some reason...

You are correct that according to the schematic, the 40 amp fuse does feed the fuel cut off solenoid directly. But doesn't this seem a bit strange? I have seen mistakes on schematics before.

I do know the fuel shutoff solenoid on my BX2200, of course a different tractor and this may be irrelevant, but it is fed by a 5 amp fuse. Since the OP has one known problem, and the 10 amp fuse blows when he tries to start the tractor with everything connected, this would seem to indicate there is a relationship between the fuse blowing and the issue that keeps the tractor from starting... It takes very little effort to move whatever is within the injector pump to cut the fuel off. Just seems like needing to supply high amperage to make this happen would not be required.
My L35 has a similar system. It has the timer (don't know if it's the same part no.) but it has a single coil solenoid, 10A fuse (I think), smaller wire size and doesn't use a relay.
Dave's schematic shows 2 sq mm wire size and a power relay, which would indicate higher current draw.
I found a discrepancy in the L35 schematic in the lighting circuit, but its all we have. If the schematic is correct, I don't think his solenoid is the problem or not the only problem.
 

Henro

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B2910, BX2200, KX41-2V mini Ex.
May 24, 2019
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My L35 has a similar system. It has the timer (don't know if it's the same part no.) but it has a single coil solenoid, 10A fuse (I think), smaller wire size and doesn't use a relay.
Dave's schematic shows 2 sq mm wire size and a power relay, which would indicate higher current draw.
I found a discrepancy in the L35 schematic in the lighting circuit, but its all we have. If the schematic is correct, I don't think his solenoid is the problem or not the only problem.
I don't know obviously, but if the tractor does not start when the solenoid is attached, and does start when the solenoid is removed, I think there is a message there... :unsure:
 

PoTreeBoy

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I don't know obviously, but if the tractor does not start when the solenoid is attached, and does start when the solenoid is removed, I think there is a message there... :unsure:
I may be reading the tea leaves wrong, but . . . The timer requires 12 volts from the ignition switch to reset. When that 12 volts is removed, the timer turns on the solenoid (through the relay) and starts timing down. If the timer never gets that 12 volts to reset due to a short/blown fuse, does it stay on? I don't know and this would require the solenoid be functioning and OP not realize it.
Edit: thinking about it more, this doesn't make sense either.
 
Last edited:

PoTreeBoy

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I think the schematic is suspect. There is no 12 volt battery connection to the timer/relay to power the relay when the key switch is off.

Here's how the L35 works. There's a 12 volt battery supply to the timer as well as the key switched supply.

Capture+_2021-02-23-16-12-17.png
 

Henro

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Equipment
B2910, BX2200, KX41-2V mini Ex.
May 24, 2019
1,252
287
83
North of Pittsburgh PA
I think the schematic is suspect. There is no 12 volt battery connection to the timer/relay to power the relay when the key switch is off.

Here's how the L35 works. There's a 12 volt battery supply to the timer as well as the key switched supply.
Well, each tractor is different...so comparing one to another is shaky...

Bottom line is it SEEMS that when the OP removes the solenoid, the tractor starts. I do not remember what he did to stop it afterwards.

With the solenoid in place on the injector pump (I think I remember this correctly) the tractor will not start.

This seems to indicate the solenoid is keeping the fuel cut off when trying to start the tractor.

Will be interesting to hear the resolution from the OP. We are all trying to do our best to help, but we are not there...
 

Justin Charles

New member

Equipment
2008 Kubota MX5000SU
Feb 22, 2021
9
0
1
Ocala, Florida
I have attached the wiring diagram I believe is for your tractor. It appears to have an OPC system for Operator Protection System..

I also marked up a portion of the wiring diagram involving the Stop Solenoid.

The solenoid has two internal coils but that is misleading as the wiring for both internal coils is tied together. The solenoid is grounded through the body. Your test of applying power might not reflect the ground connection though the solenoid body.

View attachment 55353

If your tractor has the OPC system then, when some safety switch is out of its normal position, the timer is sending a few seconds of power to the engine stop solenoid via the relay thus stopping the engine.

You comment that the engine starts with the stop solenoid removed. I suggest before you do the replacement you try unplugging the electrical connection. If a relay or timer has failed it could be powering the solenoid continuously preventing starting.

Dave
Dave - Thanks for your help ! I just received the new fuel solenoid and installed it. That didn't fix the issue. I also put a new seat safety switch in as well. Tried starting with power to new solenoid and with power disconnected. With power to new solenoid it cranks and blows a 10A fuse immediately. With power disconnected from solenoid it cranks but won't start, but does not blow fuse. Do you think the solenoid relay could be the culprit?
 

PoTreeBoy

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L35 Ford 3930
Mar 24, 2020
434
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Dave - Thanks for your help ! I just received the new fuel solenoid and installed it. That didn't fix the issue. I also put a new seat safety switch in as well. Tried starting with power to new solenoid and with power disconnected. With power to new solenoid it cranks and blows a 10A fuse immediately. With power disconnected from solenoid it cranks but won't start, but does not blow fuse. Do you think the solenoid relay could be the culprit?
Something's fishy here. Let's start from the beginning. Since you've had this tractor, has the shutoff ever worked right? If so, when did it quit working and what else happened or was changed about that time?

I suspect you got the wrong part. Yours needs power to shutoff, but many models need power to run. Can you get a part number off your old and new solenoids? Try reinstalling your old solenoid and starting your tractor with the connector off.
 

Justin Charles

New member

Equipment
2008 Kubota MX5000SU
Feb 22, 2021
9
0
1
Ocala, Florida
Something's fishy here. Let's start from the beginning. Since you've had this tractor, has the shutoff ever worked right? If so, when did it quit working and what else happened or was changed about that time?

I suspect you got the wrong part. Yours needs power to shutoff, but many models need power to run. Can you get a part number off your old and new solenoids? Try reinstalling your old solenoid and starting your tractor with the connector off.
[/QU
Dave - I've done what you suggested with the original solenoid as well as the new solenoid - disconnected power and tried to start . When power is disconnected it doesn't blow the fuse but just cranks. If power is connected it blows the fuse. Both solenoids are identical. I'm beginning to think your thought about the solenoid relay shorting out could be the problem since it's connected to the solenoid which is grounded to the engine block when in place. Unless you think of something else, I'll get a new relay from the Kobota dealer Monday and try that. Once again, I really appreciate you help and thoughts !!
 

PoTreeBoy

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L35 Ford 3930
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But the tractor still starts when you remove the solenoid?
Can you get the part number off the solenoids?