M7060 Losing Power after warming up

[clange]

Hi all,

This is my first post to this forum, but am at wits end and am hoping someone on here can give me some additional suggestions to offer to the dealer shop for diagnosing.

I've got a 2014 model M7060 with relatively low hours. It produces power very well within the first 10 minutes of starting but after it starts warming up you see a decrease in power. I first noted this when connected to my 8' Land Pride shredder, but it is also evident with nothing attached to it. I tried testing this by driving in road gear on a paved road and up a (very) slight grade. Within the first 10 minutes of starting the tractor I can achieve 19.2 mph at roughly 2500-2600 RPM. Give it about 10-15 minutes and on level ground the RPM drop off to about 2400 RPM and a commensurate decrease in speed. If I try that same grade after I notice the RPM drop off, I can no longer maintain the road speed with it dropping to 14-16 mph and RPMs dropping accordingly.

If I scroll through the LCD information screen, it appears there is a readout of the fuel usage (or at least that's what I think it is). When cold and full throttle running down the road, I see approximately 2.9 gallons per hour. As it starts warming up, it increases rather rapidly to 3.7-3.9 gallons per hour - roughly a 33% increase. I have a DPF and therefore see no black smoke.

It resided at the dealer for 2 months and all they could find was a single injector that was marginal and was replaced after quite a bit of troubleshooting. At first they thought I was nuts because they couldn't get it to act up. Of course, their dyno has been down during this time which made it more difficult for them to diagnose. The replacement of that injector marginally helped, but the problem persists. They said that they engaged Kubota and they ran a number of tests, but couldn't identify anything else that might be wrong. They seemed to be very focused on the injectors given the replacement campaign on later model injectors, but my injectors fell outside of that campaign and it sounds like the symptoms that I am experiencing are different from the failed batch of injectors.

For what it is worth, there appears to be no fuel flow problem from the tank to the injection pump and the filters have been changed.

I'm hoping someone here has some additional suggestions. I'm starting to wonder about a turbo wastegate issue, but I hesitate to mention that and send this discussion off on a tangent.

Thanks for any help or insight!

 

[Mike of Southern IL]

Watching this thread.
I have same issue with a L3200 HST. I'm leaning towards debris in the fuel tank . My tractor sits for long periods of time. Changing fuel filter helps but it reverts back to the same symptoms.

 

[WoodKutter]

I would start by eliminating fuel problems from the equation. Ensure unrestricted flow.

 

[woodman55]

The increased fuel burn is interesting.

Are the brakes adjusted properly ? JUST, a idea, but I wonder if the brakes are dragging slightly, which would heat them up, which makes them drag more, etc, ect ,ect. Can you put a load on the engine without the tractor moving ? Some form of pto driven implement would do, (generator, feed mill, irrigation pump) that would eliminate most of the drive train.

I can't see the hyd system putting enough of a load on the engine or it waiting 10 - 15 minutes, but I would not totally eliminate it.

If you own a infrared thermometer, check over the entire tractor and see if anything is abnormally hot.

 

[clange]

The increased fuel burn is interesting.

Are the brakes adjusted properly ? JUST, a idea, but I wonder if the brakes are dragging slightly, which would heat them up, which makes them drag more, etc, ect ,ect. Can you put a load on the engine without the tractor moving ? Some form of pto driven implement would do, (generator, feed mill, irrigation pump) that would eliminate most of the drive train.

I can't see the hyd system putting enough of a load on the engine or it waiting 10 - 15 minutes, but I would not totally eliminate it.

If you own a infrared thermometer, check over the entire tractor and see if anything is abnormally hot.

It's funny you mention the hydraulics. I was out monkeying with the tractor this afternoon and could re-create the issue without any load on the tractor other than driving it down the road (no implements and no weight other than my 260 lbs filling the seat). It appeared like clockwork about 10 minutes after starting and I could see a noticeable increase in the fuel consumption as I was driving. Miffed as I was, I still opted to connect a shredder and do some clean up around the place that has been lacking the last 2 months while the tractor's been in the shop. (I guess there's some upside to a severe drought as I haven't had to do any shredding while this tractor was in the shop.) The longer I ran the tractor, the worse the power loss became and merely turning the steering was was causing an observable drop in RPMs. The PTO RPMs would drop as much as 20-30 RPM at times. The steering was becoming progressively harder to operate and is making some awful noises when I turn the wheel. I'm still not sure what the problem is, but it looks like it may not be at the power producing end of the tractor. My theory is that there's something funny going on with the hydraulics and it's robbing power that would otherwise go to the PTO or the wheels. I'm not sure what could be

I didn't think about using an infrared thermometer. I may try that before it heads back to the shop. I did take some videos of the symptoms so they don't think I'm crazy.

Good point about the brakes. I've never adjusted them. It's hard to think that they'd tighten up with time, but maybe they could?

 

[Thunder chicken]

If your leaning toward a hydraulic issue, maybe try changing the hyd filters. You have to drain the oil….. it’s a 3 pail job so think about reusing as per the manual. I found a plastic container that would hold all the oil when dumped…. The WSM calls for the first filter change at 500…. Then oil and filters at 1000. When I changed mine at 500, they had a lot of rubber gasket gunk in them. I don’t know if they have a bypass in them or not? Maybe yours got an excessive amount of gasket goo and machining bits left in it. Hopefully something that simple.

I run mine in metric, but commonly see that fuel burn range you mention at WOT on the road in 6th gear up a grade. But it jumps around as the load changes despite where your foot is!

 

[whitetiger]

While your dealer had your tractor, did they perform PSB-2021-007 using Diagmaster? This should be the first step when the complaint is low power once it is at operating temperature.

I personally have found seven units that have failed the tests, installed the improved injectors and they all have good power now.

 

[Catherine57]

While your dealer had your tractor, did they perform PSB-2021-007 using Diagmaster? This should be the first step when the complaint is low power once it is at operating temperature.

I personally have found seven units that have failed the tests, installed the improved injectors and they all have good power now.

Wow, this sounds exactly like our tractor!
What is the active test that it refers to in the bulletin? Is that something that can be recreated reliably at the dealer? We have a M4-071 that runs great for the first 10 minutes or so, then drops down to lower power. It is fairly consistent.

We have a test hill. When the engine is cold, with the mower PTO set to 540 and 4th gear, we can drive up that hill and the PTO readout (easier to record than engine RPMs) stays at or above 500. But after about 10 minutes, it struggles to get up the hill in 4th gear. The PTO readout drops down to 350 - 400. It goes back up on level or downhill stretches. If we stop and let the engine cool, the tractor can again sail up the test hill with no problems.

We have changed filters and fuel, checked low pressure fuel delivery and are confident that the fuel is getting to the injectors.

My concern is that they won't be able to reproduce the failure at the dealer and thus we would see the same problem once it's back on our test hill.

Possibly related -- the other readout on the screen that I record on the test runs is the % number for that particulate filter. Last time it regenerated, it only went down to 36. As we mow, the number seems to go up pretty fast. In one hour of mowing yesterday it went from 61 to 70. Is this normal? We are approaching 100 hours.

Thanks for any advice or suggestions.

Catherine

 

[whitetiger]

Is that something that can be recreated reliably at the dealer?

The tests can be done using Diagmaster with the tractor setting in their shop.

 

[Catherine57]

Following up on my earlier post -- yes indeed our problem was the injectors. The dealer replaced all of them under warranty and it runs like new. It took a while to get it in and get the injectors, and then the weather was awful for trying it out -- too dang soggy. But we've had it out several times and it works great.

Related or not -- before when it ran a Regen it only cleaned up down to 36% or so and clogged back up pretty fast. Now it has run one Regen, all the way down to 4%, and seems to be building up much slower. I guess this would be consistent with running too rich on the bad injectors? The smoke was never black, but I guess that's the sign that the filter system is doing its job.