Hitachi 120-3 stalling

[Andy K]

Hey guys,
I’m new to the forum and having some issues with my machine. It’s been running like a champ until last weekend.

The machine has plenty of power and works exactly like it should in all functions for about 5-8 minutes. Then the hydraulic pump gets to hot to touch and starts shutting down, blowing black smoke and locking up. When it cools off, it runs great again for 5min. There was a clicking from the pump when it was running good and now there isn’t anymore clicking. The engine doesn’t gets hot before all this happens.

I’ve been reading the other posts and it’s looking like the DP sensor is bad. Unfortunately I don’t know where it is, can somebody point me in the direction of a service manual?

I’d like to check everything out before I spend a fortune on parts. I just did a complete undercarriage on it and now this.‍

Thanks,
Andy

 

[Diesel Dave]

Check your messages

 

[Diesel Dave]

The clicking sounds at the hydraulic pump are the min / max displacement solenoids maintaining the desired hydraulic pump flow. Some electrical issues will cause the PVC controller to stop sending control signals to the displacement solenoids (no more clicking) and by default the pump will go to maximum output and stay there causing excess engine pull down and stalling.
Check that the “power on“ indicator lights are flashing approx once per second on the stacked ECU and PVC controllers behind the seat. If not flashing check fuses at the fuse box. Also check the ground wire connections are clean and tight. IIRC, the ground wires are bolted down to the floor in the area of the seat pedestal.

 

[Andy K]

The clicking sounds at the hydraulic pump are the min / max displacement solenoids maintaining the desired hydraulic pump flow. Some electrical issues will cause the PVC controller to stop sending control signals to the displacement solenoids (no more clicking) and by default the pump will go to maximum output and stay there causing excess engine pull down and stalling.
Check that the “power on“ indicator lights are flashing approx once per second on the stacked ECU and PVC controllers behind the seat. If not flashing check fuses at the fuse box. Also check the ground wire connections are clean and tight. IIRC, the ground wires are bolted down to the floor in the area of the seat pedestal.

Thank you for the manual link and all the help. I pulled and checked every fuse and they were good. I’ll check for blinking lights after work today.

 

[Andy K]

Hey guys. I finally had the time to get back on it. I pulled the seat to check the grounds and everything is good.

I do not have any blinking lights on the EC or the PVC but all the fuses are good. Maybe I’m looking in the wrong location but the only place I see a red dot is on the harness connector going into the controllers.

Andy

 

[Diesel Dave]

Pic of PVC below showing “power on“ lamp location.
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[Andy K]

Pic of PVC below showing “power on“ lamp location.
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View attachment 320320

Thanks again for holding my hand through this. There was a thin layer of stuck sand over the led glass. I’m on it when I get home this afternoon.

I got a laptop with Windows 7 yesterday. Hopefully I can get the connector and a program.

 

[Andy K]

I think we’re getting somewhere. I plugged everything back in and I have the heartbeat on the EC & the PVC.

I jumped out the connector and I’m getting four codes. 4, 2 , 5, 8.

Andy

 

[Diesel Dave]

Double check your flash count , there is no code #8.
Check your messages.

 

[Andy K]

Double check your flash count , there is no code #8.
Check your messages.

Thanks again for all the help. I think we’re closing in on this.

I get four quick blinks ….pause then two slow blinks followed by five quick blinks…..pause then two slow followed by six fast then it repeats again starting with four blinks.

My son told me they’re probably (4), (25) & (26)

Everything is pointing to the DP sensor. I’ll test the voltage this afternoon.

 

[Andy K]

Hey guys. I checked the voltage on the DP sensor and this what I had.

4.8V going to the sensor.
Cold Idle: 3.7 on the back probe.
After about 5min of idle I heard a change in the engine. I jumped up and the back probe went to 0 and the hydraulic oil was hot.

I put the machine in “E & P” mode and it was 1.5 & 2.1V and at idle it was 0. I unplugged the sensor again and it was getting 4.8V. I let the machine cool down and everything repeated.

Here’s the $1200 question, should I try an aftermarket $80 sensor or buy the OE and hope for the best?

Andy

 

[Diesel Dave]

What terminal #‘s on the DP harness are you back probing, #1 and #3 ?

 

[Andy K]

What terminal #‘s on the DP harness are you back probing, #1 and #3 ?

I back probed #1 & #2 on the DP connector side.

Wire colors on the DP sensor:
#1) Black wire on one end
#2) White wire in the middle
#3) Red wire on one end

Connector unplugged:#1 & #3
Black & red 4.8v from the PVC

Back probe:#1 & #2
Black & white voltage started at 3.8v cold and went to zero when the hydraulic oil got hot…. 4-5 min at idle.

I can’t remember if I tried reading the voltage from #1 & #2 black and white from the PVC connector

After reading this it looks like I have to check the actuator pressure.The DP sensor might be going to zero to overcome it?

 

[Diesel Dave]

Did you check the DP sensor initial voltage setup ?
The original sensors were adjustable the newer ones are not .
The test harness isn’t required for the procedure below just back probe #2 and #3.

 

[Andy K]

Did you check the DP sensor initial voltage setup ?
The original sensors were adjustable the newer ones are not .
The test harness isn’t required for the procedure below just back probe #2 and #3.
View attachment 320497

I did not but I’ll remove and check it out this afternoon….if it’s not raining.

I back probe it with the key on, cold and I didn’t get anything on the meter.

 

[Diesel Dave]

Just so we are talking the same language referring to wires / terminals.
.

 

[Andy K]

Just so we are talking the same language referring to wires / terminals.
.
View attachment 320504

Yes, sir.

Harness side
#1 & #3 (red & black) 4.8V ignition key on, engine off….cold or hot

Sensor side
#2 & #3 (white & black) 3.25v when hydraulic fluid is cold. I can watch the voltage drop to 0V after 3-5min of the engine running at idle. Stays at 0V until it cools down.

 

[Diesel Dave]

Sensor side
#2 & #3 (white & black) 3.25v when hydraulic fluid is cold. I can watch the voltage drop to 0V after 3-5min of the engine running at idle. Stays at 0V until it cools down.

Spec is .45 +/- 0.2 volts.
Last ditch effort , I would try and adjust the DP.

 

[Andy K]

Thanks again for all the help.

I pulled the DP sensor and adjusted the voltage to .45v key on and installed new orings. It ran perfect for 20min and the overheating oil problem went away.

I drove it and 200ft and it fell flat on its face and stalled. I checked the DP voltage again. It’s all out of wack and will not adjust with the key on anymore.

It’s looking like the sensor is my issue. Has anyone had luck with the aftermarket DP sensors?

Andy

 

[Andy K]

I just got off the phone with John Deere. Not sure what I’m going to do now because they want $1964.00 USD for this sensor. If it was $1000-$1200 I would’ve flipped for it but it’s not happening for $2k.