Glow plug dash light and Glow plugs not working

[n4khq]

I have a 7 year old M6040, I live in north GA and don't think the glow plugs has ever worked correctly. I started having problems starting on mornings with temp in low 20s a few years ago. If it was cold enough the glow plug indicator would come on for about 1 seconds when you turned the key half way to start. Even it I turned the key off and half on several times it did not seem to help starting. It has to be really cold before the light will come on. I thought this might be normal but seems like each year it gets a little harder to start on cold mornings. It was 33 degrees this morning the glow plug indicator would not even flash and the engine had to turn over serval times to crank. I have check this forum and youtube, the relay seems to be the problem most of the time. I wanted to check with you guys before I started replacing parts.
Thanks

 

[Fordtech86]

I’m not sure on the m series but on the L series you turn the key to the left to turn the glow plugs on before cranking.

 

[russell.still.5]

I thought the same thing on my M7040. The Glow plugs will not come on until the coolant temp reaches 32* F for the Mxx40. When you turn the key there is a very slight indent just before the the starter activates. If it is cold enough they glow plugs will activate.


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[n4khq]

Thanks for the replies, Fordtech86, my M series does not turn left, I gave it a try. russell.still.5, when it is below 32 will the light stay on as long and the key is in the position you described. Mine goes off in a couple of seconds to the best of my memory.

 

[russell.still.5]

There was one time a few years ago that I got really cold ,for Alabama anyway, and the glow plugs stayed on several seconds. I think it was in the teens that morning. It was always slow to crank when it was cold but it never failed to crank.


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[n4khq]

Thanks, very helpful. That describes mine, wish I had more control over glow plugs like some of my other tractors.

 

[SidecarFlip]

I own 2 M series, both are 2002 vintage nand. When you go from the second position to the third (start) positioh here's the deal..

When you turn the key to the right the first notch, that energizes the glow plugs through the glow plug relay. The light only stays illuminated as long as you hold the key in the second position

When you go [past the second position to the third (start) position, the glo plugs are turned off and you start the engine.

At no time are the glow plugs or the indicator light receiving voltage unless the key s in the second right position.

If you think just going past the second position to start is energizing the glo plugs, thats wrong, it's not except for the second you go through the second position.

Now I know why you posted the other question about a block heater. You don't need a block heater, you need to diagnose your glo plug issue it, there is actually one.

 

[n4khq]

I think I have a problem. I have two other M series that work as you describe but the M6040 will not turn on the glow plugs unless it is below freezing. If it's below freezing they come on (glow plug indicator on dash) for a second or two before they turn off. I'm holding the key in the correct position. I remember a cold morning last year where I would turn the key to the glow plug position, waited until the light goes off and cycle it through several heating. The tractor always cranks but not quick in cold weather. Thanks for the information.

 

[tthorkil]

Someone posted this a while ago.
Re: M7040 SUHD - Glow plugs
________________________________________
Have M7040HD....do you have shuttle shift? If so....

I could not get my glow plug light to come on, and went to a lot of trouble trying to diagnose it. Come to find out, Kubota...at least on this model...has funky control of the glow plugs.

My tractor is in insulated barn, and here, the inside of that barn doesn't get near as cold as the outside. But when below freezing, my tractor would start sluggishly. Was told, and found it is true, that with shuttle shift, if you put the tractor out of gear, but put the shuttle in forward position...turn the key all the way...you have the glow plugs on, there will be no light. Hold for few seconds, pull back to neutral on the shuttle...and the 'sluggishness' starting when cold is...gone. SO...I have always since, started by manual control of the glow plugs in that manner.

 

[n4khq]

Thanks, I will give it a try in the morning.

 

[SidecarFlip]

Someone posted this a while ago.
Re: M7040 SUHD - Glow plugs
________________________________________
Have M7040HD....do you have shuttle shift? If so....

I could not get my glow plug light to come on, and went to a lot of trouble trying to diagnose it. Come to find out, Kubota...at least on this model...has funky control of the glow plugs.

My tractor is in insulated barn, and here, the inside of that barn doesn't get near as cold as the outside. But when below freezing, my tractor would start sluggishly. Was told, and found it is true, that with shuttle shift, if you put the tractor out of gear, but put the shuttle in forward position...turn the key all the way...you have the glow plugs on, there will be no light. Hold for few seconds, pull back to neutral on the shuttle...and the 'sluggishness' starting when cold is...gone. SO...I have always since, started by manual control of the glow plugs in that manner.

My M9 and my 105X are both hydraulic shuttle (the 105 is a powershift). I've never been a fan of a dry clutch for loader work, hydraulic shuttles are self adjusting and much easier to deal with.

 

[lugbolt]

These are easy to figure out.

With engine off, raise the hood and follow the upper radiator hose to where it goes to the engine. You'll see a wire connector just below where the hose goes onto the engine, remove the connector from the sensor. Then go turn the key on. Just on. Glow plug light should illuminate for several seconds. If not, you've got an issue elsewhere..

As said, the glow plugs won't "come on" until the coolant temp is 32° or below, that doesn't mean air temp, that means coolant temp....so if you used the tractor at 9pm last night and got the engine up to temp, shut it down at 930, at 0600 this morning you go out to feed the cows and you turn the key and the glow plugs won't light. It may be because the coolant temp hasn't dropped below 32° yet, residual heat from last night's tractoring.

Having been around one or two M40 series, a lot of times (especially in this are) they won't come on at all..ever...because the actual air temp doesn't get that cold for any length of time, at least long enough to cool all of that cast iron and steel down below 32°F.

I'd have to look at a wiring diagram, but I don't "think" that the glow plugs are "on" during engine cranking, which would eliminate the shuttle trick. But I may be wrong. And I dont' have a book in front of me to look at the wiring diagram. Anyone want to confirm? I DO know that some of the older standard L series DID turn on the glow's during cranking, as does my old G1900. The newer L-01's do not with the exception of the L2501, which does. On the 3301/3901/4701 you turn the key on, wait for the glow lamp to go off and then crank 'er up.

 

[Dave_eng]

Thanks, I will give it a try in the morning.

Kubota glow plug operation
In very cold weather, with the block heater plugged in, the glow plug sensor will lock out the glow plugs as it senses a warm engine.
However, starting, in these circumstances can be rough and worrisome as the engine is still inhaling very cold air.
The trick is to put the shuttle shift lever in forward and turn the key to the start position.
You will hear a relay click on. I count to 10, put the shuttle back into the neutral position and start the engine.
Makes an amazing difference.
On newer models, M7060 perhaps, Kubota realized the problem and provided software which would allow the dealer to set which sensor decided the GP on time. When owners of the M series tractors install their own block heater, they won’t get the software change and need to use the manual way to control the GP’s
I know there are GP work around on other Kubota models but I was only interested in M7040’s at the time.
I learned of this undocumented feature from a Kubota mechanic who was moving around many machines for snow clearing. It was very cold and the fact that he had no trouble getting them to fire caught my eye.

In your case the GP controller may be going bad and this manual work around should take care of starting.

I think tthorkil started to manually control his GP's after my post some time ago
Dave

 

[Dave_eng]

These are easy to figure out.


I'd have to look at a wiring diagram, but I don't "think" that the glow plugs are "on" during engine cranking, which would eliminate the shuttle trick. But I may be wrong. And I dont' have a book in front of me to look at the wiring diagram. Anyone want to confirm? I DO know that some of the older standard L series DID turn on the glow's during cranking, as does my old G1900. The newer L-01's do not with the exception of the L2501, which does. On the 3301/3901/4701 you turn the key on, wait for the glow lamp to go off and then crank 'er up.

Lugbolt
This electrical schematic is from a M7050,60,& 70 WSM

I believe it shows the GP's on during engine cranking.

Dave

 

[n4khq]

These are easy to figure out.

With engine off, raise the hood and follow the upper radiator hose to where it goes to the engine. You'll see a wire connector just below where the hose goes onto the engine, remove the connector from the sensor. Then go turn the key on. Just on. Glow plug light should illuminate for several seconds. If not, you've got an issue elsewhere..

I will test it today, Thanks

 

[n4khq]

Kubota glow plug operation
In very cold weather, with the block heater plugged in, the glow plug sensor will lock out the glow plugs as it senses a warm engine.
Dave

I don't have a block heater as of today but good to know information. I feed hay with the tractor every day in the winter. Last year when it was in the 8 degrees F, I was having a real problem starting, The light would come on if I turned the key half way to start but go off in about a second no matter what you did with the key. I had to get an electric heater and leave it blowing on the engineerings block to get it started. I don't think it has never come on by just turning the key on. My L3240HST-3 comes on with the key on and goes off when your are ready to crank as LUGBOLT described. I will remove the block temperature sensor and try with switch on, and switch halfway to start.

Thanks

 

[n4khq]

I have looked every where for the wires going to the block temperature sensor Two hoses come out of the radiator, one goes to a pump and the other to the block. I'm pretty sure there are no wires in this area.

As it get colder, I will do more testing. I will take the temperature of the freeze plug which should be a good reading of the coolant temperature.

Thanks for the advice

 

[Dave_eng]

I have looked every where for the wires going to the block temperature sensor Two hoses come out of the radiator, one goes to a pump and the other to the block. I'm pretty sure there are no wires in this area.

As it get colder, I will do more testing. I will take the temperature of the freeze plug which should be a good reading of the coolant temperature.

Thanks for the advice

Perhaps this illustration from the WSM will help you find the engine temp sensor.

Dave

 

[n4khq]

Yes the illustration is very helpful and being able to check the sensor is very helpful too.

 

[n4khq]

Thanks again for the schematic I found the sensor. We have not had much cold weather and I put it on the back burner. It was 30 degrees this morning and I had to turn it over several times to start. I will check the schematic.