EX120-2 system base pressure too low

[LACHAU]

The pressure of the system depends simultaneously on all 03 relief valves A_B_C as shown below.
You must check; calibrate all three types of valves.
You should check and calibrate 02 relief valves A & B at the same time first.
If the pressure is still not reached, we will consider the relief valve C.

As MG2361 mentioned above, it is possible that your surge relief valve has been set to a low value. You should try increasing the pressure value of surge relief valve B to see how.

 

[LACHAU]

Added for more clarity.

 

[Jason Klassen]

Alright, I tried increasing the system surge relief (B) valve first. I turned it in (tighter) a full 5 turns and it made no difference.

I then tried adjusting the overload relief valve (C) for the thumb circuit. It was around 4000 psi and I wanted it lower, around 2400 psi. I backed it out in 1/4 turn increments and it reduced the pressure by about 400 psi (28.5 kgf/cm2) each time just like the chart says it should.

This made me believe that there is something else going on. The system relief (A) was a 1/4 turn away from being bottomed out when I tried it. So someone else was obviously in there before me and 5 turns of the surge relief (B) did not make a difference.

I decided the system relief (A) was faulty so I pulled it out and took it apart. The cone shaped poppet had been pressed so hard into it's seat that the metal had deformed a little. Instead of the cone having a crisp line around it from where it contacts the seat it was more of a band.

Now since I already had it out I decided to simplify the system by putting in the 120-3 parts from my old control valve. That means I replaced the system relief (A) with a plug and I removed the surge relief (B) and installed a brand new from Hitachi surge relief. I had bought it when I was trying to figure out what was wrong with the old control valve. In the 120-3 setup the surge relief (B) turns into the main system relief.

The new from Hitachi main relief has a red paint dot on the cap. I am assuming that means it has been tested and calibrated prior to me buying it? I have not tried to adjust it at all.

So after eliminating the system relief (A) and installing the new main relief (B) I tried it again. Disappointment, I got the same 4200-4400 psi.

I get that same pressure on multiple different circuits.

I find it hard to believe that the circuit relief valves (C) could be the problem. What are the chances that I get 4200-4400 psi every time whether I try the track and swing which are external to the control valve or the other circuits like bucket ,boom and stick. It seems unlikely that the circuit reliefs in the control valve which came from a different machine match exactly the circuit reliefs on my machine (tracks and swing).

I am almost thinking that the pump is not going to full stroke/angle (24 deg) either because of the pump angle sensor or the dp sensor. I checked the engine rpm in P mode and got 2365 rpm. The spec is 2350 + or - 50 rpm.

What do you guys think? Please let me know if you see flaws in my logic.

 

[mg2361]

Unloading spool and spring OK?

 

[LACHAU]

finally, my guess is that your pump has degraded! The pistons + cylinders of the pump are worn and loose!
You try a method that is not in the book, not the official way.
fabricate a gasket to limit the minimum angle of the pump. As you restrict the pump's minimum angle which means you increase flow in relief mode, it can help increase system pressure.

 

[Jason Klassen]

Unloading spool and spring OK?

Yes, I believe the unloading valve is working fine.


Interesting solution Lachau! I am willing to try it but I have some questions first.

- If I were to add a shim to the spring on the unloading valve would that raise the pressure?

- The DP sensor in the control valve is the non-adjustable type. I have an adjustable DP sensor in my old control valve that I think I adjusted to 1.1V per Lachau's recommendation. Would installing it cause the PVC command more pump angle and raise the pressure?

- The pump was rebuilt about 50 hours of use prior to me buying the machine. I have had it apart and everything looks brand new inside. I did not measure any of the pistons or bores because I couldn't find any specs to reference.

Is it possible that the new pump parts are not very good quality and the tolerances are too loose causing it to not flow enough oil to build the right amount of pressure?

Or do new pumps need to be "broken in" so that the parts mate together better and then more pressure will be developed?

When I had the pump apart I got a local hydraulic shop to "lap" the bronze face of the lens plate to the barrel. He did it on his lathe. The picture is before he did the lapping. It's smoother now.

 

[Jason Klassen]

 

[LACHAU]

Yes, I believe the unloading valve is working fine.


Interesting solution Lachau! I am willing to try it but I have some questions first.

- If I were to add a shim to the spring on the unloading valve would that raise the pressure?

- The DP sensor in the control valve is the non-adjustable type. I have an adjustable DP sensor in my old control valve that I think I adjusted to 1.1V per Lachau's recommendation. Would installing it cause the PVC command more pump angle and raise the pressure?

- The pump was rebuilt about 50 hours of use prior to me buying the machine. I have had it apart and everything looks brand new inside. I did not measure any of the pistons or bores because I couldn't find any specs to reference.

Is it possible that the new pump parts are not very good quality and the tolerances are too loose causing it to not flow enough oil to build the right amount of pressure?

Or do new pumps need to be "broken in" so that the parts mate together better and then more pressure will be developed?

When I had the pump apart I got a local hydraulic shop to "lap" the bronze face of the lens plate to the barrel. He did it on his lathe. The picture is before he did the lapping. It's smoother now.

1/- "- If I were to add a shim to the spring on the unloading valve would that raise the pressure?" The answer is "Well, maybe it could be".

2/- "- The DP sensor in the control valve is the non-adjustable type. I have an adjustable DP sensor in my old control valve that I think I adjusted to 1.1V per Lachau's recommendation. Would installing it cause the PVC to command more pump angle and raise the pressure?" The answer is "Well, maybe it could be".

3/- Have you tried adjusting the angle sensor? Adjusting the sensor angle can also increase system performance a bit.

 

[Jason Klassen]

3/- Have you tried adjusting the angle sensor? Adjusting the sensor angle can also increase system performance a bit.

I set the angle sensor according to the instructions in the manual. It says to set the angle sensor to read 4.40V +- 0.03V when the pump is at 24 deg.

- Is there a different voltage that you have found to work better?

I tried a quick test today. I unplugged the pump angle control solenoids and let the pump angle fall to maximum (24 deg). I then put the machine in P mode and held the bucket dump over relief. The pressure easily got to 5200 psi and the engine was about to stall so I let off. If I had held it there I'm sure the engine would have stalled. Looks like the pump is plenty strong enough.

I was thinking of loosening the bolts on the angle sensor so I could adjust it while a function is over relief and in P mode. Then I could watch the pressure gauge and stop when I get 5000 psi.

- Is this a bad idea?

 

[LACHAU]

I set the angle sensor according to the instructions in the manual. It says to set the angle sensor to read 4.40V +- 0.03V when the pump is at 24 deg.

- Is there a different voltage that you have found to work better?

I tried a quick test today. I unplugged the pump angle control solenoids and let the pump angle fall to maximum (24 deg). I then put the machine in P mode and held the bucket dump over relief. The pressure easily got to 5200 psi and the engine was about to stall so I let off. If I had held it there I'm sure the engine would have stalled. Looks like the pump is plenty strong enough.

I was thinking of loosening the bolts on the angle sensor so I could adjust it while a function is over relief and in P mode. Then I could watch the pressure gauge and stop when I get 5000 psi.

- Is this a bad idea?

View attachment 287928

ALRIGHT. Just like that, move forward

 

[Jason Klassen]

We have success!

I can now reach 5000 psi with every function in P mode and the hydraulic oil up to temperature (50C).

I unplugged the pump control solenoids and let it fall to maximum angle (24 deg). I then back probed the electrical connector for the angle sensor (one probe on signal and the other on ground) and got a reading of 4.48V which is actually a little high compared to the spec of 4.40 +- 0.03V.

Next I loosened the bolts on the angle sensor and rotated it until I got a reading of 4.0V. I might have been able to get away with adjusting it to 4.2V or 4.3V but I didn't bother trying. The amount of movement it takes to make a change in the voltage output is very very small, so be careful.

Right now its making the pressure it is supposed to and I'm happy. If I end up changing it for some reason I will let you guys know.

This also confirms that the new from Hitachi relief valve was preset from the factory. I did not have to adjust it.

 

[LACHAU]

We have success!

I can now reach 5000 psi with every function in P mode and the hydraulic oil up to temperature (50C).

I unplugged the pump control solenoids and let it fall to maximum angle (24 deg). I then back probed the electrical connector for the angle sensor (one probe on signal and the other on ground) and got a reading of 4.48V which is actually a little high compared to the spec of 4.40 +- 0.03V.

Next I loosened the bolts on the angle sensor and rotated it until I got a reading of 4.0V. I might have been able to get away with adjusting it to 4.2V or 4.3V but I didn't bother trying. The amount of movement it takes to make a change in the voltage output is very very small, so be careful.

Right now its making the pressure it is supposed to and I'm happy. If I end up changing it for some reason I will let you guys know.

This also confirms that the new from Hitachi relief valve was preset from the factory. I did not have to adjust it.

congrats on your success.

 

[mg2361]

Great job Jason! It is fascinating how little a change in the angle sensor adjustment can make such a big difference in performance. We have many Deere solutions (bulletins to those who don't speak Deere) on angle sensor adjustments and how they affect performance.

 

[joelx777]

We have success!

I can now reach 5000 psi with every function in P mode and the hydraulic oil up to temperature (50C).

I unplugged the pump control solenoids and let it fall to maximum angle (24 deg). I then back probed the electrical connector for the angle sensor (one probe on signal and the other on ground) and got a reading of 4.48V which is actually a little high compared to the spec of 4.40 +- 0.03V.

Next I loosened the bolts on the angle sensor and rotated it until I got a reading of 4.0V. I might have been able to get away with adjusting it to 4.2V or 4.3V but I didn't bother trying. The amount of movement it takes to make a change in the voltage output is very very small, so be careful.

Right now its making the pressure it is supposed to and I'm happy. If I end up changing it for some reason I will let you guys know.

This also confirms that the new from Hitachi relief valve was preset from the factory. I did not have to adjust it.

Amazing work Jason! I have the same machine (John Deere 490e is the Hitachia 120-2/3 body with a JD engine). It sounds like you are pretty advanced in your knowledge on this machine, I posted a newbie question on a weak boom function issue, perhaps you may have some tips?

https://www.heavyequipmentforums.co...ohn-deere-490e-excavator.102996/#post-1156073

 

[soul197106]

hi - why did you blow into the distributor? I have an ex120-3 m, and it seems to me that I have the same problem as you! I tried blowing into the main hole, in theory, nothing should pass through, everything should be sealed, or I'm wrong ?!)with your finger on the video, you are checking whether there is an air (pressure) leak somewhere

 

[Jason Klassen]

hi - why did you blow into the distributor? I have an ex120-3 m, and it seems to me that I have the same problem as you! I tried blowing into the main hole, in theory, nothing should pass through, everything should be sealed, or I'm wrong ?!)with your finger on the video, you are checking whether there is an air (pressure) leak somewhere

Yes, I put air pressure into the control valve (distributor) through the oil inlet to check for leaks.

With the control levers in neutral the oil flow is blocked by the main spools and the unloading valve. The unloading valve is supposed to bypass oil when 284 psi is reached. Mine was only reaching about 240 psi.

The air pressure I put in was only 100 psi so if everything was good there should have been very minimal leakage.

As you can tell from the video there was quite a bit of air coming out. I assumed there must be cracks for that much air to bypass the unloading valve. The unloading valve itself looked fine so there had to be another way for the air to get out.

A local wrecking yard told me that cracks in the travel circuits were common in these machines and that's when I decided to buy a new (used) control valve.

Air also leaked from the new one but not as bad. I compared them to each other by putting a pressure gauge in the airline right before the air entered the control valve. The new one held more pressure.

After installing it the new control valve reached the required 284 psi and the tracks responded much better.

Hope that helps. Its a lot of work to take out the control valve just to test it with air but I had ran through every other test imaginable so it was the only option left.

 

[soul197106]

did you lose the main relief valve or the entire distributor?

 

[soul197106]

Thank you for the answer

 

[Jason Klassen]

did you lose the main relief valve or the entire distributor?

I replaced the entire main control valve (distributor).

The control valve actually splits into 2 pieces after removing the 4 big allen headed bolts.

One side has bucket, boom, arm and auxiliary spools and the other has the main relief/unloading valve, swing and both travel spools.

I think I could have gotten away with replacing just the side with the main relief in it but nobody is willing to sell just one half of a control valve.

 

[soul197106]

thank you very much