M5030su will not run/revv up after warming up.

[TeamPSI]

My grandfather bought a M5030su at an Ag auction last winter. The tractor was sold advertised as in good running condition. From the exterior, it looked to have been worked pretty hard, but is in solid condition. We have had plenty of issues with small things like hydraulic lines to the attachments, worn and leaky cylinders, and the other usual stuff.

The engine purrs like a kitten and cranks perfectly every time when the machine is cold. Everything works, and the tractor drives and operates exactly as you would expect it to.

After reaching normal operating temperature, the engine will seem to begin to not want to accelerate. It seems as if the engine wants to stay at an idle. You can move the accelerator handle or foot pedal but the engine will not revv up. If you move the accelerator all the way to slow, you the engine will
usually die out. As long as the accelerator is moved forward somewhat, the engine will idle. Nothing that I do seems to make any change in this condition other than letting the machine cool down. If you let the tractor sit for about an hour, it will crank and run perfectly again. Once it gets warmed up, but at no exact specific rate or time, this issue will always happen again. It seems that the hotter it is outside, or the more that we were to machine, the faster that the issue will present itself. The engine is running at a little less than halfway on the temperature gauge when this happens. Nothing seems to be overheated at all.

Sometimes, it seems as if you are able to keep the engine running at a fast RPM that it will stay revved up as long as you do not move the accelerator or cause the engine to go dead. If you allow the engine to lose its speed, it will become stuck at idle and you can move the thrall you want, but nothing is going to change until the machine cools off.

It really seems as if either the engine is not receiving any fuel even though the linkage to the fuel pump is moving, or that something is keeping the engine from revving.

I am definitely not a tractor mechanic, but can definitely follow directions. I am at a loss in this situation though, as I do not really know where to start. I have searched around quite a bit, and the only thing that I could even find that sounded similar was some guys talking about the fuel injection pump relay possibly being bad, but I am unsure of that.

Does anyone here have any experience with anything like this?

 

[skeets]

You might want to change the fuel filter, for starters and then check the fuel lines to see if its is collapsing,, it do happen,, you might need to go through the whole thing changing all the filters and new oil as well. That's where I would start simple things first

 

[Tooljunkie]

My want to check valve adjustment also. Especially if it has lots of hours in it. Likely never adjusted.
Air filters may need to be looked at too. Should have inner and outer filter.

 

[TeamPSI]

Thank you for the quick reply.

Your response jogged my memory. We did take the tractor to the local Kubota dealer and described the issue to him. He replaced the fuel filter. He told us that he use it for a while and could not get it to re-create the problem again (I know that he just did not run or work it for very long or it would of happened for sure).

The oil was changed at this time as well as the air filters.

It seems so strange that everything runs perfectly, and I mean perfectly up until the point where the issue happens. I could see something like a collapsing fuel line being the problem for sure, but I do not believe that clogged air filters filters or anything of that nature to be the issue. I would not be surprised if the valves had never been adjusted, and would assume that they probably should be by now, but again I do not see how valves being out of adjustment would cause an almost instantaneous change in the way that the engine is performing or reacting to our input. again, I am not a diesel mechanic and would be completely oblivious to as to whether or not valve lash settings would cause the engine to stop running once it heated up. I know about gasoline engines, and I do not think that valve adjustments will present this type of symptom. The engine does not make any odd noises were run strangely at all up until this happens.

I do not remember seeing any rubber fuel line that could have been collapsing, but will check through it again. I have not been the one to service this tractor, so I am only somewhat familiar with it at this point. I know how it runs and drives, but as far as the mechanics of this actual machine, I have not delved into it too far.

The tractor is definitely in running condition. All of the small parts that are serviceable have been service recently. This has to be something small ...

 

[Tx Jim]

Ditto changing fuel filter. I also suggest check to see if tank is venting and good fuel flow from tank to inj pump.

 

[Tooljunkie]

Fuel tank not venting?
Diesel engines run 375 psi or better for compression, valves not sealing as engine heats up could be a possibility, but more likely it would run rough before shutting down.

 

[TeamPSI]

I removed the fuel cap while the issue was occurring and try restarting, etc. Venting the fuel tank seemed to have no effect on the issue.

One of the hydraulic hoses for the front loader busted yesterday, so it may be a couple of days before I'm able to test again. The worst part of it all is that you have to use the tractor a lot before it happens. It's hard to spend a couple of hours just trying to re-create a problem, then trying to figure out what it is before the tractor cools off and works fine again. … Crazy

 

[ShaunRH]

Wait, you have to run the tractor for a couple of hours or work it real hard to get the problem to happen?

That seriously sounds like fuel flow. Air would be an issue at any time, hot or cold. Compression would also be an issue any time but usually WORSE for mal seating valves when cold over hot (where they would happily expand and fit their seats nicely, unless the stems are lengthening which is more than an 'adjustment'. Valves usually wear down, not expand along the shaft. It should be throwing white smoke with bad valves as well.)

So, my bet is you have a borderline fuel flow problem. You could test for it when the problem is happening with a vacuum gauge just before the injection pump, but likely you have a bad lift pump or a blockage somewhere in the lines. I'd tear down the fuel lines, check for anything in them, clean the tank and all the filters along the path. Replace any bad or checked lines (could be air seepage) and make sure any water separators are clean and clear.

Just my $0.02 on the matter and it is not worth that much either.

 

[North Idaho Wolfman]

After reaching normal operating temperature, the engine will seem to begin to not want to accelerate. It seems as if the engine wants to stay at an idle. You can move the accelerator handle or foot pedal but the engine will not revv up. If you move the accelerator all the way to slow, you the engine will
usually die out. As long as the accelerator is moved forward somewhat, the engine will idle.

Is your model Serial# <51139 ?
If it is I've got some good news for you... I know exactly what's wrong!
There is a funny little and rarely used device called a compensator and it does exactly what you talking about, controls heated idle and acceleration.
Sounds like you have something wrong with yours!
Here is what your dealing with it's inside the plate for the throttle and governor.

 

[turck]

Is your model Serial# <51139 ?
If it is I've got some good news for you... I know exactly what's wrong!
There is a funny little and rarely used device called a compensator and it does exactly what you talking about, controls heated idle and acceleration.
Sounds like you have something wrong with yours!
Here is what your dealing with it's inside the plate for the throttle and governor.
View attachment 11993

sounds like you are on the right track, I was suspecting something electronic was getting lazy like a fuel solenoid.

 

[TeamPSI]

Shaun,
Yes, this only happens after at least 45 minutes, but usually longer. I would say that the average time to re-create the issue is 45 minutes-1 hour of normal usage.

Wolfman,
The serial number of the machine is 560801. Model number 195.
The engine model says S-2802-DI-A

If I am reading your response correctly, then my model number is not the one that you're talking about.... Right?


Turck,
I had read on another form about a fuel solenoid possibly sticking closed when the engine was warm. Again I do not know a lot about diesels, so did not know if the fuel actually flowed through a solenoid/switch controlled line or not. Does the fuel solenoid on this engine actually control the opening/closing of a valve within the solenoid itself or does this just actually control electrical power to something else? When I think of a "fuel solenoid" I think of a large relay/switch that actually has fuel flowing through it and a gate that opens and closes when power is applied. Something like a nitrous fuel solenoid for racecar. Is this what the diesel engine has.. More or less?

One of the only things that I'd do know for certain about a diesel fuel system is that it is hard to re-prime it if you take it apart. If I tear the system down, will I need to have any special tools or knowledge to re-prime the system? This is not even my tractor and it does work correctly for a little while, so my grandfather doesn't hardly even notice that this happens. When we decide to borrow it though, it always happens to us because we are actually putting it to some real use.


The problem definitely has to do with something opening/closing or getting plugged up inside of the fuel/throttle delivery. I drive a lot more with the foot pedal than my grandfather does, so I seem to notice the problem more than he does. When I use the tractor, I will leave the hand throttle set to a slow speed, and while I am driving I will increase the throttle when needed by use of the foot pedal. My grandfather is more quick to just revv the engine up and leave it there while driving with the clutch. His other tractors do not have put throttles on them so he is used to leaving the rpm's constant and driving with his feet.

As an imaginary example,, if you were to revv the engine up to PTO speed and leave it there, you could possibly never notice that this issue even happens unless you overworked the machine and caused the engine to die out.

 

[North Idaho Wolfman]

Well your serial # 560801 is Greater than serial#51139 so it should have it.
In the picture there is #130 that is a thermostat and I would suspect your problem revolves around this device being bad.
Real simple to tell if it has a compensator, just look at the top of the throttle plate, it will have two shafts if it has a compensator and only one if it does not.

As far as the stop solenoid you have a passive type, it's an external magnetic pull type that is triggered by the key being turned off, the key switch triggers a control timer that turns off after approximately 5 seconds, So I don't think that has anything to do with your problem.

Throttle plate with Compensator:

Throttle plate without Compensator:

Stop solenoid: Note this was an option, you may or may not have one,
Do you stop the tractor with the key or with a pull rod?

Optional stop solenoid:

 

[TeamPSI]

Well your serial # 560801 is Greater than serial#51139 so it should have it.
In the picture there is #130 that is a thermostat and I would suspect your problem revolves around this device being bad.
Real simple to tell if it has a compensator, just look at the top of the throttle plate, it will have two shafts if it has a compensator and only one if it does not.

As far as the stop solenoid you have a passive type, it's an external magnetic pull type that is triggered by the key being turned off, the key switch triggers a control timer that turns off after approximately 5 seconds, So I don't think that has anything to do with your problem.

Throttle plate with Compensator:

Throttle plate without Compensator:

Stop solenoid: Note this was an option, you may or may not have one,
Do you stop the tractor with the key or with a pull rod?

Optional stop solenoid:

Unfortunately only one of those photos/attachments works for me. I can see the throttle plate with compensator but that's it. I do see 130 in the diagram though, and if that is a thermostat, than that definitely seems to make some sort of sense.

The engine does not turn off with the key. You must pull the manual lever to kill the engine.

 

[TeamPSI]

Now that I have looked over the parts diagram a little more and have thought about what is happening and what that thermostat is doing in the throttle plate, I think that you are right Wolfman. I am very tempted to order this thermostat right now.

Would it be possible to ask if there is anything else that I'm going to need for this job? I've never removed apart from this tractor, especially in this area so I do not know which gaskets or other materials/supplies may be needed. If it is as easy as taking apart a few bolts and putting it back together, then it should be a snap.

Why can't this thing just have a carburetor? ;-) ;-) ;-) ;-)

 

[TeamPSI]

Here are some photos of the pump area that I took today. I must be honest and tell you that I do not know exactly what I'm looking at.

Can you point me to the location of the throttle plate or compensator?


...and by the way thank you for the help thus far.

 

[North Idaho Wolfman]

I reloaded the pictures, have no clue what happened to them????

I can tell you a couple of things from the pictures that you posted, Sadly it doesn't look like you have the compensator, I only see one shaft and I see two bolts for the adjustment of the high and low end.

Also you don't have a fuel stop solenoid on your tractor, so you have to stop it by pulling the rod and not just turning off the key.

We will have to switch gears and look for other possibilities.
I would double check the rubber fuel lines.
I would pull the lift pump and check the diaphragm for damage.
If there is nothing here, your next steps for repair are not so easy or cheap!
It involves some serious work and serious tear down to get to the governor assembly.
Have there been any change in the amount of oil in the tractor, like fuel is getting into the oil?
Also if it hasn't been a while, I would consider an oil and filter change before I went too far.

In the next pic is all noted:
Red is the throttle plate
Blue are the rubber fuel feed lines to check
Yellow is the lift pump (low pressure, low flow fuel pump)
Green is where the stop solenoid would hook up if it had it.

 

[TeamPSI]

I reloaded the pictures, have no clue what happened to them????

I can tell you a couple of things from the pictures that you posted, Sadly it doesn't look like you have the compensator, I only see one shaft and I see two bolts for the adjustment of the high and low end.

Also you don't have a fuel stop solenoid on your tractor, so you have to stop it by pulling the rod and not just turning off the key.

We will have to switch gears and look for other possibilities.
I would double check the rubber fuel lines.
I would pull the lift pump and check the diaphragm for damage.
If there is nothing here, your next steps for repair are not so easy or cheap!
It involves some serious work and serious tear down to get to the governor assembly.
Have there been any change in the amount of oil in the tractor, like fuel is getting into the oil?
Also if it hasn't been a while, I would consider an oil and filter change before I went too far.

In the next pic is all noted:
Red is the throttle plate
Blue are the rubber fuel feed lines to check
Yellow is the lift pump (low pressure, low flow fuel pump)
Green is where the stop solenoid would hook up if it had it.

View attachment 12031

Okay thanks it makes more sense looking at it now, knowing that what I'm looking for is not really there. Thank you for showing me which part is which.

I have squeezed and pinched the rubber lines while the issue is occurring and didn't notice any difference, but that really doesn't say much. I will pull both lines and check for good flow through them.



I have not actually monitored the oil in the tractor myself, but I know that it was changed once since it was bought and that was about 6 months ago when we had the local dealer attempt to diagnose and fix this issue. They change the oil, filter, and the fuel filter from what I know. Are you saying that I should check the oil for contamination with fuel? I don't want to go too far off into a subject that might not be the actual problem but how could that happen?

I have the feeling that the seller of the tractor knew that this issue was occurring when they took it to the auction. Anyone who test drove the tractor would never have experienced it. Lucky us.

 

[North Idaho Wolfman]

The reason to check for fuel is that if the injection pump is failing that can be an indicator of that failure, but I don't think that is your problem.

You are looking at only a few possible reasons that the tractor is having the problems you've described.

First is a long shot, Start at the lift pump, pull it off the motor 2 bolts and nothing to worry about falling in the motor on removal. Once off the tractor pull the bolts off the round cover and remove the diaphragm and check for any damage, hold it up to the light and look for pin holes, if there is any thing that doesn't look good, I would just change the whole pump, there is a $10 difference between just the diaphragm and the whole assembly.
Pump: 15263-5203 $52.51
Gasket: 1A021-52140 $0.88

Next is the stop plate, remove the 4 bolts and pull the plate off the side, your going to be checking foe free spring loaded operation, make sure the spring is not broken.
Gasket: 1A021-51660 $2.78

Next is throttle plate, pull the 2 bolts and 2 nuts off of the throttle control plate and pull up gently, there is 2 springs (one inside another) attached to the throttle connection internally (you should be able to see the other side of the attachment threw the stop plate hole), I tie a string to the springs before removal to prevent them from falling into the motor, once springs are string tied pull them off the throttle arm.
I'm hoping that one or both springs are broken, missing or stretched so there would be your problem.
After you remove the throttle plate look down the hole to the governor and there should be another spring in there (do not remove that spring just verify it is there and connected on both ends). You should be able to move the governor back and forth with it returning smoothly, if not then we will have to go to the next stage.

If any of the springs are stretched, broken, damaged, or missing then there is your problem, you should be able to replace the springs and fix your issues.
Gasket: 1E147-57210 $2.16
Spring one: 17301-56410 $3.24
Spring two: 17301-56420 $2.78

 

[TeamPSI]

Wow, thanks. You are awesome.

I will take a look at it and update the thread ASAP.

 

[TeamPSI]

Due to the way that life has unfolded over the past year or so, we actually never got a chance to take the tractor apart. I had to use a tractor yesterday to dig up a busted water line.

It was so hot outside… The tractor did the same old thing and after it got hot, it would barely idle and would not increase rpm no matter where the throttle position was.

I just thought it was funny that we were stranded by the same tractor again, years later, same problem, FML.