Troubleshoot excavator not tracking straight. Yanmar VIO 50

[jrhook111]

So I took it out on a straight section of road and timed it to gauge it's speed. I discovered that the deviation to the right (still have the pumps reversed) is bad enough that I need to fix it. I'm going to couple the pump outputs together. I figure if it causes any issues with the rest of the machine operating, I can put a manual valve there and just open it when I have to track long distances. I doubt that will be an issue. Since we will be coupled together, it really won't matter where the accumulator is. Speed was pretty good, even having to correct direction several times. I calculated 2.4mph, spec is 2.9, and if it were going straight I would have been very close to that.

So that's my solution. Thanks guys.

Bibendum, on my little joyride I tested to see if the boom could lift the machine alone, and it does, no problem. Maybe check the relief valve pressure you are getting with your boom function. The PRV on that valve might be too low.

 

[uffex]

Good day Jr
As I have interpreted your most recent post with those lines crossed we still have the problem but has it switched to the other side?

 

[Bibendum]

Good to hear (kind of) JR. Too bad the pump is on its way out, but maybe you can find something in the mean time while you can still run the machine.

I'll just reiterate my symptoms-

- Lack of power when tracking / pushing material
- No difference when high speed is selected while traversing an incline
- Negligible difference when high speed is selected on flat ground
- Lack of power in left track compared to right track (this was not as apparent in my machine compared to JR's by the sounds of it, as the machine did not have a noticeable drift when traveling so i did not choose to bring it up, however it was apparent)
- Boom alone will not raise/pitch machine without help from other functions

*Ive verified and resealed system reliefs.
*Ive verified case drain of each travel motor
*Ive verified condition of swivel joint
*Ive verified pilot pressure
*Ive verified mechanical operation of travel valve linkages
*Ive verified operation of high speed travel (both electrically and hydraulically)
*Ive verified there is no restriction in return flow to tank
*Ive verified, as well as possible without removing valve bank for further inspection, the condition and operation of the main cut off control valve

Uffex's point of reduction in flow in one side of the pump verses the other made good sense. Since I also had a somewhat lazy track, swapping lines seemed like an easy way to test as the fault should move to the other track. Swapping lines showed a transfer of the lazy track from the left to the right side, which to me, narrows the issue down to the pump. I will not say this is definitive yet, and plan to drop by a friends place to flow test each side of the pump.

Assuming each pump in either machine is worn, i am of the opinion that JR's pump has more significant wear on one side of the rotary group versus the other, while the wear is more even across both rotary groups, however still slightly more pronounced on one side, in my machine.

I believe it would make sense that we do not see a reduction in system pressure due to the "horsepower control" capability of the pump, up to a point. Referencing the chart I've attached, the maximum force "F2" has remained constant due to the system reliefs, maintaining the capable pressure. Load "F1" has, in 3 of four scenarios, never changed, and the pump is still capable of suppling system pressure. However due to wear either in the pistons, barrel, valve plate or a fatigue in the spring, it supplies this pressure at a reduced flow rate, which is most noticeable while tracking, especially in high speed.

So I did what i was apprehensive to do from the get go, I turned swash plate adjustment screw in, by 1/4 turn increments to a max of 3/4 from original setting, and monitored system relief pressure, where there was no change. This may be an indication that the spring did not fatigue. The pump now takes in more fluid by volume, making up for the bypass. The machine now tracks at an acceptable speed and has no issues pushing material.

I'm not considering this a fix until i flow test the pump. If it checks out, ill boil it down to the spring fatiguing over time and in that case, i'm not too worried about it. If the flow test shows a poor result, Ill begin a search for a pump or a rebuild kit if available (price dependant). In the mean time, I've some jobs to do, so if it pumps, it digs.

Im simply stating my thoughts here. If you see any flaw in my logic please point it out and correct me. Id rather be just dumb, not dumb and ignorant.

 

[jrhook111]

Good day Jr
As I have interpreted your most recent post with those lines crossed we still have the problem but has it switched to the other side?

Yes, it switched sides, but it is not as bad as it was before. Still needs fixing though.

 

[jrhook111]

Good to hear (kind of) JR. Too bad the pump is on its way out, but maybe you can find something in the mean time while you can still run the machine.

I'll just reiterate my symptoms-

- Lack of power when tracking / pushing material
- No difference when high speed is selected while traversing an incline
- Negligible difference when high speed is selected on flat ground
- Lack of power in left track compared to right track (this was not as apparent in my machine compared to JR's by the sounds of it, as the machine did not have a noticeable drift when traveling so i did not choose to bring it up, however it was apparent)
- Boom alone will not raise/pitch machine without help from other functions

*Ive verified and resealed system reliefs.
*Ive verified case drain of each travel motor
*Ive verified condition of swivel joint
*Ive verified pilot pressure
*Ive verified mechanical operation of travel valve linkages
*Ive verified operation of high speed travel (both electrically and hydraulically)
*Ive verified there is no restriction in return flow to tank
*Ive verified, as well as possible without removing valve bank for further inspection, the condition and operation of the main cut off control valve

Uffex's point of reduction in flow in one side of the pump verses the other made good sense. Since I also had a somewhat lazy track, swapping lines seemed like an easy way to test as the fault should move to the other track. Swapping lines showed a transfer of the lazy track from the left to the right side, which to me, narrows the issue down to the pump. I will not say this is definitive yet, and plan to drop by a friends place to flow test each side of the pump.

Assuming each pump in either machine is worn, i am of the opinion that JR's pump has more significant wear on one side of the rotary group versus the other, while the wear is more even across both rotary groups, however still slightly more pronounced on one side, in my machine.

I believe it would make sense that we do not see a reduction in system pressure due to the "horsepower control" capability of the pump, up to a point. Referencing the chart I've attached, the maximum force "F2" has remained constant due to the system reliefs, maintaining the capable pressure. Load "F1" has, in 3 of four scenarios, never changed, and the pump is still capable of suppling system pressure. However due to wear either in the pistons, barrel, valve plate or a fatigue in the spring, it supplies this pressure at a reduced flow rate, which is most noticeable while tracking, especially in high speed.

So I did what i was apprehensive to do from the get go, I turned swash plate adjustment screw in, by 1/4 turn increments to a max of 3/4 from original setting, and monitored system relief pressure, where there was no change. This may be an indication that the spring did not fatigue. The pump now takes in more fluid by volume, making up for the bypass. The machine now tracks at an acceptable speed and has no issues pushing material.

I'm not considering this a fix until i flow test the pump. If it checks out, ill boil it down to the spring fatiguing over time and in that case, i'm not too worried about it. If the flow test shows a poor result, Ill begin a search for a pump or a rebuild kit if available (price dependant). In the mean time, I've some jobs to do, so if it pumps, it digs.

Im simply stating my thoughts here. If you see any flaw in my logic please point it out and correct me. Id rather be just dumb, not dumb and ignorant.

View attachment 285787

Bibendum. To my farmer brain your thinking seems sound. I like the idea of compensating for the bypass by adjusting the horsepower control. But let's see what Uffex thinks.

 

[uffex]

Good day
Both the pumps regulators are connected as one alter one alter the other. From what I have been able to establish from a trusted source that the issue revolves around the valve plate porting. Not something we can play with only make an after fix - hence linking the main lines when you select high speed tracks.
I am thinking on the lines that a simple cheap solenoid valve hooks the lines together when you select high speed tracking. What is your opinion?
Kind regards
Uffex

 

[jrhook111]

Good day
Both the pumps regulators are connected as one alter one alter the other. From what I have been able to establish from a trusted source that the issue revolves around the valve plate porting. Not something we can play with only make an after fix - hence linking the main lines when you select high speed tracks.
I am thinking on the lines that a simple cheap solenoid valve hooks the lines together when you select high speed tracking. What is your opinion?
Kind regards
Uffex

I thought about putting in a solenoid so I could control it, but first I'm just going to hook them together and see how it functions. I've ordered the fittings. I'll report back.

 

[uffex]

Thats great I dont think you will need anyting larger than 3/8"

 

[uffex]

Good day
I have taken a look at the wiring schematic. I must admit it is a little confusing.
The solenoid that controls the motor displacement according to the diagram is hooked up to s second safety switch. Can you straighten this out for me? What switch do you have in the cabin?
Kind regards
Uffex

 

[jrhook111]

That control lockout is the handle on the left that must be pushed down to operate the machine, like pretty much all excavators have. The high speed travel functions is a pedal that is held down and it actuates a hydraulic control valve.

 

[uffex]

Good day
I must point out that hooking the main lines together at the pumps may have an adverse effect on the remaining circuits, to avoid this as much as possible will be a compromise.
Making the connection to the two forward travel lines would give straight travel in the forward direction but not in reverse. This would be my suggestion, there would as to the best of my research little benefit in pump rebuild - replacement. If you get the correct track speed is a strong indication that the pump is giving the correct flow, pressure is simple to confirm.
Kind regards
Uffex

 

[jrhook111]

Good day
I must point out that hooking the main lines together at the pumps may have an adverse effect on the remaining circuits, to avoid this as much as possible will be a compromise.
Making the connection to the two forward travel lines would give straight travel in the forward direction but not in reverse. This would be my suggestion, there would as to the best of my research little benefit in pump rebuild - replacement. If you get the correct track speed is a strong indication that the pump is giving the correct flow, pressure is simple to confirm.
Kind regards
Uffex

I'm still waiting on parts to couple these lines together. I ordered fittings for the main lines at the pump which won't fit the travel lines, so that's what I'll be trying first. I'll see if it affects the other operations of the machine too much.
If I were to hook the travel lines together after the control valves, I would have to put a valve in the coupling that I could control from the operator seat. Because if that valve was open and I only moved one travel lever, the machine would respond by tracking straight. I wouldn't have independent control of the tracks in forward with the lines coupled.
So I'm thinking if I am going to need to put in a valve that can be controlled from the cabin I might as well do it at the main pump lines. That way I can travel forward or reverse straight, and with the valve closed it won't change anything with the rest of the machine. Also, there's a lot more room to put the new hardware in near the pump than there is under the floor pan.
I'll let you guys know how it goes once I get the parts.

 

[uffex]

Good day
That's is a good plan, it's great you have a good understanding and know the pros & cons.
Kind regards
Uffex

 

[jrhook111]

Good to hear (kind of) JR. Too bad the pump is on its way out, but maybe you can find something in the mean time while you can still run the machine.

I'll just reiterate my symptoms-

- Lack of power when tracking / pushing material
- No difference when high speed is selected while traversing an incline
- Negligible difference when high speed is selected on flat ground
- Lack of power in left track compared to right track (this was not as apparent in my machine compared to JR's by the sounds of it, as the machine did not have a noticeable drift when traveling so i did not choose to bring it up, however it was apparent)
- Boom alone will not raise/pitch machine without help from other functions

*Ive verified and resealed system reliefs.
*Ive verified case drain of each travel motor
*Ive verified condition of swivel joint
*Ive verified pilot pressure
*Ive verified mechanical operation of travel valve linkages
*Ive verified operation of high speed travel (both electrically and hydraulically)
*Ive verified there is no restriction in return flow to tank
*Ive verified, as well as possible without removing valve bank for further inspection, the condition and operation of the main cut off control valve

Uffex's point of reduction in flow in one side of the pump verses the other made good sense. Since I also had a somewhat lazy track, swapping lines seemed like an easy way to test as the fault should move to the other track. Swapping lines showed a transfer of the lazy track from the left to the right side, which to me, narrows the issue down to the pump. I will not say this is definitive yet, and plan to drop by a friends place to flow test each side of the pump.

Assuming each pump in either machine is worn, i am of the opinion that JR's pump has more significant wear on one side of the rotary group versus the other, while the wear is more even across both rotary groups, however still slightly more pronounced on one side, in my machine.

I believe it would make sense that we do not see a reduction in system pressure due to the "horsepower control" capability of the pump, up to a point. Referencing the chart I've attached, the maximum force "F2" has remained constant due to the system reliefs, maintaining the capable pressure. Load "F1" has, in 3 of four scenarios, never changed, and the pump is still capable of suppling system pressure. However due to wear either in the pistons, barrel, valve plate or a fatigue in the spring, it supplies this pressure at a reduced flow rate, which is most noticeable while tracking, especially in high speed.

So I did what i was apprehensive to do from the get go, I turned swash plate adjustment screw in, by 1/4 turn increments to a max of 3/4 from original setting, and monitored system relief pressure, where there was no change. This may be an indication that the spring did not fatigue. The pump now takes in more fluid by volume, making up for the bypass. The machine now tracks at an acceptable speed and has no issues pushing material.

I'm not considering this a fix until i flow test the pump. If it checks out, ill boil it down to the spring fatiguing over time and in that case, i'm not too worried about it. If the flow test shows a poor result, Ill begin a search for a pump or a rebuild kit if available (price dependant). In the mean time, I've some jobs to do, so if it pumps, it digs.

Im simply stating my thoughts here. If you see any flaw in my logic please point it out and correct me. Id rather be just dumb, not dumb and ignorant.

View attachment 285787

Hey Bib. Did you ever flow test that pump? Any updates?

 

[Bibendum]

Hey Bib. Did you ever flow test that pump? Any updates?

JR, I haven't had the chance no, have been working the machine. I did crank the pump up some more though. If you push enough material with it i imagine i can just about get it to stall, so i just go easy on it. So far it has dug 3 utility trenches and grubbed and levelled a yard. Not being able to use the blade on these little excavators to their full potential is quite a pain. In my opinion it really is what makes the smaller machines efficient.

It looks like there are rebuild kits around for them. After talking to a few colleagues I think theres a good chance that the pumps can be freshend up by tearing them apart, removing the scratches on a flat lap and then lapping the two faces together. If the pistons / barrels are shot it needs a full rebuild, unless they are sleeved.

 

[jrhook111]

So this was an unexpected result. I hooked the pumps together where the lines exiting the pump, and I thought that would make it track straight but also have some changes to the digging controls in how they function together. Several things happened:

First, you can't drive one track at a time with the pumps tied together. When the track control lever is in neutral, there is a passage for flow from the pump to get back to tank. When you push the lever forward, the path to tank is closed and oil is forced to the travel motor. With the pumps tied together, when I push the left travel control, the oil just all goes through the right control valve neutral passage, and vice versa. The only way to turn is to do one track forward and one reverse at the same time. When you push one lever only, absolutely nothing happens.

Second was expected, but worse than I thought it would be. The digging functions are totally screwed up with the pumps tied together. Like the tracking, you must be doing 2 functions or nothing happens, and it's basically impossible to simultaneously control the curl and stick properly like we are all used to.

And third, it did NOT track straight! It went left again. Recall it went left initially, so I swapped lines at the travel motors and it switched to the right, therefore I eliminated the travel motor as the cause. I also swapped lines between the directional valve and the swivel, and it switched again, tracking right, which eliminated the swivel as the cause. I thought it was the valve, but then swapped lines directly at the pump and found it again switched to the right, so we concluded it was the pump. (However, in this configuration, it didn't seem to be deviating right as much as it had in the original setup.) Tying the pumps together should provide equal pressure and flow to both control valves and therefore both travel motors, but it went left again. With any pump differences eliminated, that means the deviation I am seeing now is probably from the control valve, travel motor, or both.

Essentially, the only way to really fix this from what I can tell would be to put in new components, which is not going to happen due to cost.

Finally, I want to ask about what Bibendum did, turning up the horsepower control at the pump. I'd like to try that to compensate for internal leakage in the pumps, but I don't want to cause any damage. Obviously if the engine is straining noticeably then it's too high, but I have a feeling that might help my situation a bit too. What are the risks of turning that up? How would I determine that it was at a good level, or if it was too high?

 

[uffex]

Good day
Screwing up the equipment was much as I would expect however I would expect the measure to straighten out the crab crawling. I would suggest the following lift each side of the track frame and measure how much pressure is required to drive each side as well as measure the rotational speed in both directions. Some detail has been missed. We need to go over this once more.
Kind regards
Uffex

 

[jrhook111]

I'm not sure it's worth more troubleshooting at this point, because I think I've definitively proven that there are multiple simultaneous problems. Correct me if I'm wrong: Given that when I change the pump connections the tracking changes from left to right, the pumps are obviously performing differently. Follow that with when I tie the pumps together eliminating any difference there, I am now tracking left again, which means the control valve and/or travel motor are contributing to the problem too. Recall that with the pumps reversed, it did not deviate to the right as bad as it had been deviating left. So the pump discrepancy on one side and the valve/motor on the other canceled each other out somewhat. I think that is the configuration I am going to leave it in. Agree with my thinking?

The reality is that I would have to put in a new pump, new control valves and a new travel motor to truly fix the issue, and the problem just isn't bad enough to justify that level of cost.

What do you think about adjusting the horsepower control of the pump? What should I check to make sure I do this properly?

Cheers,
Jon

 

[jrhook111]

So I tried adjusting the horsepower control. I checked the speed on tracking over 100 meters and then adjusted the control by 1/4 turn increments. After 4 adjustments I was 1 full turn in, and I had only improved my speed by 2 seconds, hardly any difference at all, and the tracking issue did not change. I'm reluctant to adjust it further because I'm not sure if it could cause harm, but the engine never sounds like it is straining at all. Until I can learn more, I just put it back where it was.

 

[uffex]

Good day Jon
For a more pernament fix plumb the two forward main lines together with a solenoid valve.
I will make some information for you.
Kind regards
Uffex