Hitachi EX Hydraulic Pump Control Problems

[bdward]

I have a EX100-3 with a classic slow pump control situation. It starts with everything operating at about 50% speed and gradually slows down to dead slow. I've checked the wiring and the control modules are both blinking red. The engine is operating fine and in checking the pump pressure, I get 800 psi for the pump delivery pressure when in neutral. Under a load, the main relief pressure jumps to 6000 psi. That tells me an ok pump but no stroke flow to run things.

I don't have access to a Dr EX so for me it's hit and miss.

I have another EX120 I can borrow parts off of so I exchanged the two pump displacement solenoids and tested the machine. Now I have lots of flow and everything works fast but it tries to kill the engine if I'm not real careful. Now when I test the pump pressures I get 2500 psi at high idle neutral operation and 4600 psi under a load just short of killing the engine.

Question: Is the next logical culprit the A sensor? I can adjust it within it's limits but I'm suspecting it's probably bad. If I replace it does the sensor simply slip in and out per page T04-05-06A or can something fall out on me. It's not easy to see back in there. Is the referenced punch mark easy to see or is a 180 degree problem possible? Can I adjust this by "ear" without using the voltmeter?

Question: To replace the pump displacement solenoids, is the correct OEM part# 9147260?

Question: Does the P-Sensor play a direct role in the operation and should I exchange it from my 120 to check it?

Question: Does the N-Sensor play a direct role in the operation and should I exchange it from my 120 to check it?

Thanks for your help and appreciate your input.

Bill

 

[mg2361]

Without some sort of diagnostic software, special test harness' or some very time consuming voltage measurements your only choice is to shotgun parts at it.

operating at about 50% speed and gradually slows down to dead slow.

I exchanged the two pump displacement solenoids and tested the machine. Now I have lots of flow and everything works fast but it tries to kill the engine

This tells me either the solenoids or the circuitry has issues. If you have no/slow hydraulics and swap out the solenoids and now you have stalling, then maybe disturbing the wiring created an issue??

Can I adjust this by "ear" without using the voltmeter?

Absolutely not. Must be adjusted with a meter. It does just slip out. Just watch for the little spring clip on the shaft.

is the correct OEM part# 9147260

Yep

Question: Does the P-Sensor play a direct role in the operation

Question: Does the N-Sensor play a direct role in the operation

Both do. They are used for the anti-stall by the PVC.

 

[bdward]

Thanks for the info. I don't know the history on this machine. With all these sensor failing, I'm questioning whether a voltage spike occurred somewhere along the way? The EC motor control & sensor have also failed & currently are replaced with a hand throttle. Will the lack of feedback from the EC motor sensor affect my diagnostics at this point? I've checked the voltage while running at the battery & register 29 volts now. Could there be a unregulated voltage from the alternator getting thru to the system. The Niko alternator doesn't have the external regulator to check as outlined in the manual. I'll keep swapping parts from my other EX and hopefully won't damage them.

 

[mg2361]

Will the lack of feedback from the EC motor sensor affect my diagnostics at this point?

No it should not.

I've checked the voltage while running at the battery & register 29 volts now

Getting a little high. Battery good? Overcharging or excessive AC ripple can play he-- on a computerized system.

I've checked the wiring and the control modules are both blinking red.

Once every second? Might want to read the manual on accessing codes using the PVC's blinking light to see if there are any stored codes that might lead you in a direction.

 

[bdward]

Both control modules blink regularly on a one second interval. Batteries good. I'll check voltage output at alternator to confirm output.

I don't have the ST7139 harness to intersect the voltage reading at the A-sensor harness. Which of the prongs on the machine harness are used to find the 4.4 volts? With 3 prongs it shouldn't be too hard to figure out.

This is a relatively low hour machine so it's not wore out but it was exposed to an ocean side environment for awhile. I checked all the wiring plug-ins pretty close for issues and found some white scum which I cleaned but no rot through.

 

[mg2361]

I don't have the ST7139 harness to intersect the voltage reading at the A-sensor harness. Which of the prongs on the machine harness are used to find the 4.4 volts?

The test harness I was referring to is for the pump displacement solenoids (see below). You don't need a test harness for the A sensor. Just backprobe the angle sensor connector. Terminal 1 is the 5 volt reference, terminal 2 is the signal wire and terminal 3 is the return (ground) wire.

 

[bdward]

I checked the A-sensor harness as you described and got 4.99 volts. My plan is to order a new A-sensor and tap wires into the terminal 1 & 3 so I can adjust to the 4.4 volts. I traded out the P-sensor with no change. I'll get the new valve solenoids, A-sensor, and N-sensor installed and hopefully see improvement. Am I missing anything? Do you think it's OK to leave the 29 volt alternator on the machine? - Thanks

 

[mg2361]

When measuring the voltage on the "A" sensor you need to have your meter connected to the signal wire (terminal 2) and ground (or the return wire terminal 3). When you make an adjustment that is the voltage that will change. The 5 volt reference (terminal 1) will always read 4.9 - 5.1 volts.

 

[bdward]

Thanks, I'll let you know how it turns out when I get the new part.

 

[Topsi]

I am very new to this form, my friend bought an ex120 digger and is havig these very same problems, as I not up to speed with all these solinoid valves etc could anybody out there recomend where i get a manual for this machine. Thanks

 

[kj.fahey]

The test harness I was referring to is for the pump displacement solenoids (see below). You don't need a test harness for the A sensor. Just backprobe the angle sensor connector. Terminal 1 is the 5 volt reference, terminal 2 is the signal wire and terminal 3 is the return (ground) wire.

View attachment 238585

Would you be able to explain in more detail how I can test the angle sensor harness without the special harness, I think that is the Problem with my machine I have a ex200lc-3

 

[kj.fahey]

Would you be able to explain in more detail how I can test the angle sensor harness without the special harness, I think that is the Problem with my machine I have a ex200lc-3

I want to be able to see the output voltage so I can make the adjustment because the tech who put mine on in the first place didn’t program it

 

[kj.fahey]

Also wondering how to make the adjustment, thanks

I want to be able to see the output voltage so I can make the adjustment because the tech who put mine on in the first place didn’t program it

 

[mg2361]

Would you be able to explain in more detail how I can test the angle sensor harness without the special harness

By backprobing (carefully). It can be checked without the special harness.

Also wondering how to make the adjustment, thanks

Loosen the angle sensor. Start the engine. Disconnect the two pump control solenoids. Let the engine idle for about 5 minutes (until the voltage stops changing). Then you adjust the angle sensor to the voltage spec. Tighten the angle sensor making sure the voltage does not change during tightening. Shut machine off. Connect pump solenoids.

 

[kj.fahey]

Thank you, so in order to change the sensor voltage you have to do what exactly? Turn the end of the sensor that sticks out or?

 

[mg2361]

I see you have been posting on multiple threads. That is too confusing. Please try to keep all your questions to your thread.