PC390 lc-10 Hydrulic pressure issues.

[Ez2nv240]

2015 pc390-10 data plate has been wiped off so no serial number available.

Machine is sluggish compared to a pc390-11 that’s on site. Like noticeable slower. 4 seconds extra to lift boom, twice as long to “curl bucket” machine has a shear attachment not a bucket.

Over the last year the company has had issues with over hearing Hydraulics. Valve body started leaking, pulled valve body sent out for “reman” which was only a reseal from what I can tell. Replaced pumps do to failure, low pressure and low volume.

Now on to current problems. Machine won’t allow me to calibrate pumps. Comes back with a E-5 and C-1. Pump pressure of calibrated pumps below standard value and PC-EPC current is out of specified range.

As of right now the pumps are outputting 6,000-6,500 psi when held on relief valve according to gauges. According to monitor it’s only seeing 4,800-5,200. The actual gauge reading is off through out the range vs the monitor. Service limit is 4,800-5,333. So the relief valve is out of range. But what is causing the difference in gauge vs monitor? Three separate gauges all varying the differences.

Also engine rpm is low service limit and standard are 1930 +/- 100 rpm. Currently it’s around 1750-1800.

I’ve followed the book diagnostic and have gotten no where. What’s could cause the monitor/computer to read way lower pressure then actual?

 

[Simon C]

My guess is that the sending unit that the monitor goes off of is defective or the wiring in between is corroded or loose connections. Loose connections will lower voltage so the monitor would react from that.
Simon C

 

[DustAndRay]

Agree with Simon. That gap between actual gauge and monitor reading is a sign of a dying pressure transducer or corroded signal wire. Had something similar on an older Hitachi. My problem ended after cleaning up every ground connection and replacing the pressure sensor. On your RPM issue, 1750 vs 1930 is a real problem and could be making everything worse. Low RPM means your pumps never hit full flow/pressure even if they're good. Worth checking your throttle motor/actuator and fuel system. Also, E-5 + C-1 on a PC390 usually means the controller gave up on calibration mid-cycle. Hard to complete cal when RPM and pressure are both out of spec at the same time.

 

[Ez2nv240]

Agree with Simon. That gap between actual gauge and monitor reading is a sign of a dying pressure transducer or corroded signal wire. Had something similar on an older Hitachi. My problem ended after cleaning up every ground connection and replacing the pressure sensor. On your RPM issue, 1750 vs 1930 is a real problem and could be making everything worse. Low RPM means your pumps never hit full flow/pressure even if they're good. Worth checking your throttle motor/actuator and fuel system. Also, E-5 + C-1 on a PC390 usually means the controller gave up on calibration mid-cycle. Hard to complete cal when RPM and pressure are both out of spec at the same time.

So according to the diagram the “fuel knob” sends signal to the pump controller, then to the engine controller. So my current thought is the pressures aren’t right for what it should be doing so pump controller isn’t telling the engine to rev up because it doesn’t think it’s needed.

 

[Simon C]

A new sensor may fix it, but you may need to get a schematic for it and test the wires that feed the sensor from their source for strength with a light bulb. That is the sensor end disconnected and the source disconnected at computer to see if harness can handle power or not.
Would need to see schematic to follow the wire back. The ground and positive power could easily be tested for voltage drop with reference to the battery positive 24 volt and negative post.
Simon C

 

[LACHAU]

2015 pc390-10 data plate has been wiped off so no serial number available.
.....
Also engine rpm is low service limit and standard are 1930 +/- 100 rpm. Currently it’s around 1750-1800.

I’ve followed the book diagnostic and have gotten no where. What’s could cause the monitor/computer to read way lower pressure then actual?

First of all, I want to talk about engine speed.
How did you check the engine speed to get the data you mentioned?
Please note that there are three ways to check the engine speed, as shown in the attached image.
Next, have you measured the voltage supplied to the sensors? If so, what is it in volts? It should be 5V normally

 

[Simon C]

First of all, I want to talk about engine speed.
How did you check the engine speed to get the data you mentioned?
Please note that there are three ways to check the engine speed, as shown in the attached image.
Next, have you measured the voltage supplied to the sensors? If so, what is it in volts? It should be 5V normally

View attachment 357625
View attachment 357624

Such good info to determine if there is actually a problem, or is it just a recording problem caused by faulty sensor or wiring problem.
Simon C

 

[John C.]

How many hours are on this machine?
My first impression goes to the control valve being removed for rebuild? A hydraulic valve is not something you rebuild like an engine or transmission. You can reseal leaks with the valve left in the machine easy enough. You can change cartridges, seals and springs without removing the valve. The valve and the pumps are components of a load sensing system. Engine performance is the first consideration. A load sensing system is based on the output of the performance of the engine. The output performance of the pumps are also directly affected by the actions of the valve and its components. The OP says the pumps were replaced due to failure and doesn't state what the failure was. Did something break or was there visible excessive wear and did it happen in both pumps or just one or was there a broken drive and on and on. So were the pumps replaced because of reduced performance caused by problems in the control valve that were not fixed when it was removed from the machine. What is also not mentioned is the use of a flow meter to calibrate the pumps. I've followed up many machines over my years that were "rebuilt" by local shops only to find that they didn't have a test stand even capable of properly calibrating the output levels of the pumps they were rebuilding. Many times all that was done was new aftermarket bearings and seals and nothing done to the regulators at all.

At this point I would normally just start over and confirm proper operation of each component. Is the engine making its designed horsepower? Were fuel strainers, filters and the air intake system serviced? Make sure there are no fault codes in the electronics. If those are cleaned up, then flow test the pumps with a flow meter. Once you know the pumps are working right then go back into the valve and make sure all the components in it are working properly.

 

[Ez2nv240]

Sorry for the lack of responses. Other machines failure have taken priority needing to be fixed first.

Engine rpm was gathered by on board computer. Engine speed was measured at no load and against relief. Against relief is what I mentioned.

I have not measured voltage at a sensors yet. I did repair some wiring that was damaged to no effect either way. Probably won’t be back on said machine until next week.

 

[Ez2nv240]

How many hours are on this machine?
My first impression goes to the control valve being removed for rebuild? A hydraulic valve is not something you rebuild like an engine or transmission. You can reseal leaks with the valve left in the machine easy enough. You can change cartridges, seals and springs without removing the valve. The valve and the pumps are components of a load sensing system. Engine performance is the first consideration. A load sensing system is based on the output of the performance of the engine. The output performance of the pumps are also directly affected by the actions of the valve and its components. The OP says the pumps were replaced due to failure and doesn't state what the failure was. Did something break or was there visible excessive wear and did it happen in both pumps or just one or was there a broken drive and on and on. So were the pumps replaced because of reduced performance caused by problems in the control valve that were not fixed when it was removed from the machine. What is also not mentioned is the use of a flow meter to calibrate the pumps. I've followed up many machines over my years that were "rebuilt" by local shops only to find that they didn't have a test stand even capable of properly calibrating the output levels of the pumps they were rebuilding. Many times all that was done was new aftermarket bearings and seals and nothing done to the regulators at all.

At this point I would normally just start over and confirm proper operation of each component. Is the engine making its designed horsepower? Were fuel strainers, filters and the air intake system serviced? Make sure there are no fault codes in the electronics. If those are cleaned up, then flow test the pumps with a flow meter. Once you know the pumps are working right then go back into the valve and make sure all the components in it are working properly.

12,000 hours on machine. Pumps were replaced due to low output, as mentioned. Flow and pressure were low.

 

[John C.]

Impressions: The hydraulic system is load sensing. You need to confirm what your are reading on the monitor panel for pressures. They might be load sense pressure. The way the system is supposed to work in that load sense pressure is suppose to be kept within about 300 PSI in the older model machines and I suspect it is the same with this one. Load sense pressure is the pressure your read in the circuit beyond the main control valve which goes back to the pump governor controls. If there are no fault codes, then the problems are almost always in the load sense system. The older machines you could reset the TVC pressure to change the output of the pumps. Load sense pressure comes from all the functions which are connected in the control valve through a load sense circuit. In the older machines they used pressure compensated lift check valves generally known as compensators and there were problems all the time with those. When I worked for the dealers we changed those all the time to fix the performance issues.

 

[Marcrus]

You need to do full hydraulic pressure checks, very common for the 10-11 machines to loose power over time, I found around 8000hrs they get extremely bad. Check the pilot pressure and correctly set it first, then mains, then go through and set ls and PC valve, PC could be bogging down your stall rpm speed. The 10-11 is very touchy with ls 1bar low is significant. Pumps won't match either I worked out years ago you need to swap arm in and out epc connectors around to resolve the issue as the pump controller packs off pilot pressure to the spool for fuel/HYD savings took ages to prove it through internal tech support etc.
Running a shear as well will degrade the pump life badly too. Do hydraulic checks and report back