Hitachi ex 120-3 hydraulic issues

natemarine · Apr 18, 2020

Hello

For a few years now I and several mechanics have been trying to get to the bottom of this issue on my excavator. It began as a load on the hydraulics you can hear when you start the machine. Starts and sounds normal, then the hyd system loads up and you can hear it put a load on the engine. For a period of time, surging the right track would return the system to normal load, only to return in 3 seconds. It also used to have worse problems in fall and winter but went all summer with no problem. Now it has manifested into a problem of mayor power loss, the machine will stall/deadhead at the with most functions tracks and stick seem to be affected the most. Replaced pilot pump, rebuilt pilot valve, both full of debris and not functioning properly. To my amazement this did not solve the issue. Replaced 2 leaking cylinders that may have discharged the debris into the system also. Just ordered dp sensor, angle sensor, high speed solenoid, but we are guessing. It is an asian machine and biggest problem is I can't find specs for it or plug in to it for diagnotsitcs because it is grey market. Another off symptom I'v noticed is that when machine sits on a steep incline while working it works correctly for a period of time. Yesterday I was letting it idle after getting pilot pump and everything back on and the engine idle excellerated on it's own with the hydraulics safety lever still in off position. It did it again so I climbed in the cab and the green lights on the dash were dim and flickering. Alternator has been tested. I could really use some advice, can't replace the machine just yet got to get back to work.

mg2361 · Apr 19, 2020

Welcome to HEF natemarine

!

natemarine said:
Replaced pilot pump, rebuilt pilot valve, both full of debris

This could be the entire problem. What kind of debris? Did you take pictures to share? Did you check the suction screen in the hydraulic reservoir? Drain reservoir and inspect the bottom for debris? Cut open the hydraulic filter and inspect for debris as well as the pilot filter. If the debris got spread through the system then it could be causing various functions, solenoid valves, etc to operate intermittently.

Next time your instrument lights act up, disconnect the blue/yellow wire from the alternator and ground it to see if that resolves the light issue. If not then connect the wire back to the alternator.

natemarine · Apr 19, 2020

Thank you... I dont have any pictures unfortunately. It was pieces of plastic in the pilot pump probably from the bucket and boom cylinders we were thinking but I don't really know where it came from....Bucket cylinder was in bad shape and I ran it that way for a bit not knowing any better. The pilot valve had clogged ports and had alot of buildup inside. The guy who rebuilt it was a pro I was not the one. The filters were visually inspected, but not cut open, reservoir not drained. We are going to get into the cab and inspect all wiring and harnesses etc. tomorrow.

natemarine · Apr 19, 2020

mg2361 said:
Welcome to HEF natemarine!

This could be the entire problem. What kind of debris? Did you take pictures to share? Did you check the suction screen in the hydraulic reservoir? Drain reservoir and inspect the bottom for debris? Cut open the hydraulic filter and inspect for debris as well as the pilot filter. If the debris got spread through the system then it could be causing various functions, solenoid valves, etc to operate intermittently.

Next time your instrument lights act up, disconnect the blue/yellow wire from the alternator and ground it to see if that resolves the light issue. If not then connect the wire back to the alternator.

ok sorry I'm new at this forum I wasnt sure if I had to quote you in my reply to send an alert

natemarine · Apr 21, 2020

Have cheked all wiring and fuses and harnesses. Replacing the dp sensor high speed solenoid and angle sensor today, but I'd like to know what the next step should be....

mg2361 · Apr 22, 2020

natemarine said:
Replacing the dp sensor high speed solenoid and angle sensor today,

Just replacing those parts will mean nothing unless they are properly adjusted. If not properly adjusted they could make the problem worse.

natemarine said:
I'v noticed is that when machine sits on a steep incline while working it works correctly for a period of time

Is there debris in the tank?

If your hydraulics are under load at start up then swap the solenoid assemblies on top of the pump to see if your hydraulics change.

natemarine · Apr 22, 2020

When we swapped the solenoids everything sounded right.....the engine engaged quickly when touching the levers, instead of slowly revving up and having a load....it fixed the problem by sound but all the functions were super slow ..... does this tell us something? Also any advice on adjusting?

I only had one new one to replace. They are the same solenoid correct?

natemarine · Apr 22, 2020

Also when I bought this machine the line from the pilot pump used to pulse, I am reading here that that is normal, my machine no longer does this....

I have no manual but I just ordered a hard copy I hope its the right thing it is a technical shop manual for hitachi 120-3 it supposed to be here next week but any advice you could give to keep us going would help

natemarine · Apr 22, 2020

Id be happy to talk on the phone if its easier/faster
my #443-677-2324 I text too.....Nate

mg2361 · Apr 22, 2020

natemarine said:
.it fixed the problem by sound but all the functions were super slow ..... does this tell us something?

natemarine said:
I only had one new one to replace. They are the same solenoid correct?

Yes the 2 solenoids are the same. If you had aggressive hydraulics before swapping and then had weak hydraulics after swapping then one of the solenoid valve assemblies are defective. I believe you mentioned aggressive hydraulics in your original post. Did you have aggressive hydraulics before the swap?

natemarine · Apr 22, 2020

I don't know if I'd call them aggressive but fast like normal, maybe a little faster than normal

natemarine · Apr 22, 2020

to clarify, when they were switched the functions were clearly different, all of the hydraulic problems seemed to go away by ear. but functions were slow. When switched back it went back to the same old problems. Does this mean one was bad? or both? I had one new one we used to check them. I'ts still on there.

dieseldog5.9 · Apr 22, 2020

Take a look behind the seat and the computer should have a light on it, I forget now how the light works but if memory serves me right it has to do with power to ecm, there are a couple fuses in there, 1 amp DO NOT PUT ANY OTHER FUSE IN ITS PLACE.

How Fast the functions run, or their touchyness/aggressiveness can be adjusted.

I purchases a tool to read codes on hitatchi at one point for similar issues.

Debris in the pilot pump...... The pilot pump shifts the swashplate, maybe corelated, there is a pilot filter to look at.

The service manual will tell you to check the arm atatched to the sensor on the pump is attatched.

mg2361 · Apr 22, 2020

natemarine said:
When switched back it went back to the same old problems

If old problems were stalling when activating a function, then yes there would be a defective solenoid valve.

natemarine · Apr 22, 2020

dieseldog5.9 said:
Take a look behind the seat and the computer should have a light on it, I forget now how the light works but if memory serves me right it has to do with power to ecm, there are a couple fuses in there, 1 amp DO NOT PUT ANY OTHER FUSE IN ITS PLACE.

How Fast the functions run, or their touchyness/aggressiveness can be adjusted.

I purchases a tool to read codes on hitatchi at one point for similar issues.

Debris in the pilot pump...... The pilot pump shifts the swashplate, maybe corelated, there is a pilot filter to look at.

The service manual will tell you to check the arm atatched to the sensor on the pump is attatched.

1. My main sympstoms are dead heading and stalling the engine when, tracking, lifting weight aggressively, or extending the boom stick or bucket cylinders all of the way. It coincides with extra vibration, black smoke when it labors, hydraulics bleed off, when sitting stationary. I can hear a load on the hydraulics on cold start after 3 sec.
2. I would buy that tool if I knew it would work but this is a grey market machine.
3. Also the pulsing I used to hear in the pilot pump doesnt exist any more I hear this is not right
4. I did a test I see alot of people recommending on here. Switched the solenoid valves on main pump and there was a change. I hear this indicates a bad solenoid. One was replaced with a new one, I'm unsure if this is the issue but about to order another new to be sure they are both operational.

I will look for a light, to clarify you mean behind the seat on the computer itself not the instrument panel corrrect?

natemarine · Apr 22, 2020

mg2361 said:
If old problems were stalling when activating a function, then yes there would be a defective solenoid valve.

my apologies I just got this laptop and can't figure out how to cut and paste yet lol
further details above but basically the original issues were
it would stall when a load was put on it, black smoke, and stall if you lift too heavy of weight or track without pausing, or extend any of the cylinders on the boom all of the way

I didn't have out of the norm fast movements or anything

natemarine · Apr 22, 2020

also I did check all the fuses.... and...they were all fine assuming they were all in the correct spot I have a diagram I'm going to confirm. I took the bottom plate off and cleaned the two main grounds but they were probably fine. The two computers in the back have an active red flashing light on each one.

dieseldog5.9 · Apr 22, 2020

Yes these can be head scratchers, sounds like your pumps arent shifting, which:
A) The internals of the pump arent shifting (mechanical issue)
B) The Sensing system is not picking up that it needs to shift, Dp sensor, Angle sensor.
C) The the Control side is not shifting the pump, Pump Solenoids

The Dp sensor is expensive from Deere, however I have bought aftermarked DP sensors and they where junk.

rgl726 · Apr 22, 2020

natemarine said:
Hello

For a few years now I and several mechanics have been trying to get to the bottom of this issue on my excavator. It began as a load on the hydraulics you can hear when you start the machine. Starts and sounds normal, then the hyd system loads up and you can hear it put a load on the engine. For a period of time, surging the right track would return the system to normal load, only to return in 3 seconds. It also used to have worse problems in fall and winter but went all summer with no problem. Now it has manifested into a problem of mayor power loss, the machine will stall/deadhead at the with most functions tracks and stick seem to be affected the most. Replaced pilot pump, rebuilt pilot valve, both full of debris and not functioning properly. To my amazement this did not solve the issue. Replaced 2 leaking cylinders that may have discharged the debris into the system also. Just ordered dp sensor, angle sensor, high speed solenoid, but we are guessing. It is an asian machine and biggest problem is I can't find specs for it or plug in to it for diagnotsitcs because it is grey market. Another off symptom I'v noticed is that when machine sits on a steep incline while working it works correctly for a period of time. Yesterday I was letting it idle after getting pilot pump and everything back on and the engine idle excellerated on it's own with the hydraulics safety lever still in off position. It did it again so I climbed in the cab and the green lights on the dash were dim and flickering. Alternator has been tested. I could really use some advice, can't replace the machine just yet got to get back to work.

Did you replace all the parts with the original hitachi parts? Specialy the pump solenoids? Did you set the angle sensor correctly? China made parts wont solve the problem on electrical side.

This machine is very complicated and fragile to handle.

Did you check also the pilot pump pressure reading?

Is the pvc computer working properly?

Did you check the wiring continuity for all the sensors and solenoids?

mg2361 · Apr 23, 2020

natemarine said:
Switched the solenoid valves on main pump and there was a change

natemarine said:
to clarify, when they were switched the functions were clearly different, all of the hydraulic problems seemed to go away by ear. but functions were slow. When switched back it went back to the same old problems.

Then maybe the wrong solenoid was replaced?

Hitachi ex 120-3 hydraulic issues

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