Komatsu pw130 1997 and ls epc valve output from pump controller

[jth]

We have been tracking problem with this unit for some time. Related on stalling on bigger load.

After checking pilot pressure and ls pressure, we noticed that ls epc pressure does not chage at all. Based on shop manual it should. Output voltage for ls epc valve is only 7V, mA values seems to be ok. With travel speed epc valve it gives 24 and 0-1000mA, just like maual says.

Cables are replaced and ok. Is there any other option than bad pump controller? There are a change that wires are broken between hO1 and pum controller, they just like to be ok.

-Janne

 

[mikebramel]

Well that is an output of the computer. Are you sure that the inputs to the computer are not giving it that base to go off of?

 

[John C.]

As I recall a PW machine is on tires, correct? A PW machine in travel mode is always maxed out. Would you describe the operational problems in a little more detail?

 

[jth]

Yes, it is on tires.

After checking voltage without solenoid wire connected, pump controller gives 24 V. It was my mistake to think that there is still 24V under load.

Machine has two epc solenoid valve's, one for ls and another for travel. So we did change them. Now travel does not work, but ls started to work like shop manual says. Travel line also has separate override valve. It gives always max flow to travel pedal.

We did order new epc valve.

Now it works very well untill it gets normal operating temperature, sometimes much longer. Depending of how hard job it is doing. Some finitializing job is ok for all day.
Machine seems to have problem if you run cylinder in to end and pressure rise near by relief pressure. Also fast travelling makes motor rpm to go up and down all the time. I'm thinking that ls differential pressure and tvc valve outpressure are not right. Some one is adjusted them before us. Could this be a reason for this behave?

Thank you for information

 

[John C.]

From what you are describing this sounds like a Dash 6 hydraulic system. The LS differential pressure should be somewhere around 300 PSI difference between the pump outlet pressure and the LS signal pressure from the main control valve. In my experience though that reading is not very critical. The system will work with nearly any difference. As I recall the TVC only comes into play when pressures and flows go over the horsepower of the engine.

If someone has tampered with the pump settings I'm thinking you have to go back to establishing the base line output of the pump. You will need a service manual and some study time to understand how the system works and what the pumps should be doing in certain operating situations. It could be that the pump settings were changed to make up for a weak pump.

The last PW machine I worked on was a PW90-5 and was basically a Dash 3 hydraulic system so I'm not sure how much more info I can provide.

Let us know what you find.

 

[jth]

Yes, it is Dash 6 from 1997.

LS Differential pressure
It was under those values in ls_input.png, 25bar if pedals neutral, 12 bar if travel pedal fully operated.

LS valve output pressure
About 1/2 of pump pressure. Only difference was "travel pedal fully operated and wheels under no load"-pump pressure was 160 bar, not 80 bar like manual says.

Pilot pressure was about 30 bar

Problems starts when temperature from tank line is about 54C.

Also check TVC-valve. It is not quite clear how it works. I was thinking that it should give bigger mA-value if motor rpm goes down. If all pedals are neutral, it gets 800mA by pump controller. How it should work?


-Janne

 

[jth]

Now I have been testing with gauges for some time. All measurements and adjustment is done. Temperature of tank line stays under 55C.
Only thing what was found is relief pressures. There are two settings for main relief, one for travel (350bar) and another for digging (325bar). Digging relief pressure was about 338 bar. Now it is adjusted to 310 bar for testing. Swing motor safety valve is still not checked.
Strange thing is that sometimes motor starts to stall even with lower pressures. Like 220 bar of main valve pressure. It just need pressure raise and little bit of movement, like it does not know how much oil it should pump. This never happens with only travel.

Another way to make this issue is that you drive some piston to end after 1-2 hour of operation. Before that it works ok. First pump destrokes before relief pressure, then pressure starts to wonder near by relief and motor starts to struggle.

So, now I'm confused. Quite sure it is not motor. It has been tested before.

Is it pump or is it some main valve issue? It looks like that pump pumps small amount of oil somewhere with pressure and it does not want to destroke. That is only thing what would somehow explain that the pressure does not raise near by relief. But why it takes so hard for motor? Anyway, TVC mA starts to raise, but it is too far behind.
What you say? Pump or something else?

 

[John C.]

It sounds like something is intermittently causing the pump to not destroke. How many hours do you have on this machine? Do you get the machine used or have you had it for a long time and it suddenly started having the problem?

 

[jth]

Machine has about 10500h. I have had it for two years now. It had that problem when I bought it. Previous owner did not get it fixed. I'm not sure when it is started to behave like that.
I did call local komatsu dealer to look at it when it arrived. They said that it is pump issue. I did take the pump out and delivered to them. They said that pump is ok but LS valve unit is guite worned. They also did change some part inside of LS valve. New seals, I think. After that the result was same, then they say it is a electrical problem.
Also there was nothing in oil filters.
Only another thing is that previous owner have used hyraulic oil in it. Not 10W-30 like manual says.

I do not want to buy a pump for a check. Is there any other way to find the reason for this behave?

 

[John C.]

Can you post a photo of the pump so I can see which one it is?

 

[jth]

ttp://komatsupartsbook.com/#?k=!0!1!5281!50!54
pump is 708-1L-00032. Komatsu made, not kawasaki.

Is there any way to check is it pump issue or something else?

I can get real pictures from the pump next week

Thank you for helping me with this

 

[jth]

Compensator valves seems to be same kind. No identification marks at all. Attachent is a picture from bucket dump compensator valve. It is same kind than travel should be. This one does not have ball and plug inside. It looks like someone has changed them long time ago.

It is worned too. Could this lead to malfunction?

 

[John C.]

Usually when the compensators start leaking internally the LS differential pressure becomes the signal of the leaking circuit and the pumps destroke. Basically the machine would be slow on most all the functions and the engine would never lug down. I seem to remember that there were different compensators depending on the function they were installed on.

You might swap that compensator with one from the travel and see if there is a difference. You pump looks like the early style with the pilot pump mounted on the back.

Does this machine have a computer and a monitor panel with a digital display. Have you checked for fault codes?

 

[jth]

Yes. This is opposite problem compared to this compensator issue. After few hours of hard work operation, everything changes faster and machine starts to have stalling problems. Stalling problems when pump is near that phase it needs to destroke.

I check another compensators too. It is clear that all original are same. Manual says that current compensator type is used on travel.

I hoped that the computer is the issue. But no error codes on monitor panel, output mA are same than computer says they should be. Only issue on that side is that monitor panel and engine throttle controller says that they are for 120, not for 130.

So what would be the reason that prevents pump to destroke? Flow somewhere between main valve and cylinder? If pressure in LS-line starts to get higher and no oil is flowing to actuator, pressure should just rise to relief and that is ok? Now it starts to have problems with lower pressures, like 200 bar. Computer has some part of this. Based on previous messages and monitor panel output, I’m thinking that it increase mA to TVC-valve and make pump to destroke.

 

[John C.]

What I've seen on pumps with long lives is small pieces of debris and grit get into the passages and make the little pistons get sticky. It also wears on them so they can also get loose and leak by causing problems like you are experiencing. Since the pump has the capability to draw the engine down I don't think you have a problem in the piston and barrel assembly. More likely you need to pull the controls off the pump, open them up and clean them out real well.

What does you monitor panel in the cab look like?

 

[jth]

Update for an old thread. I have not done anything for the pump, just doing summertime jobs. This have to be done before next season.

One new thing has come out. I did change place of temperature meter. Now it is installed on top of main valve. Temperature keep raising even above 65 degrees (Celsius). I have cleaned radiator and it is ok. Strange thing is that input hose to radiator does not feel as hot as main valve. Is this normal and how these radiator works? Is there some kind of thermostat or valve to control oil flow to radiator/tank

 

[jth]

Problem is solved.
EPC and LS pistons were worned. Reason for oil temperature was located on pilot pump. Pump was tested on test bench.
If someone have problems with these (Komatsu build) pumps, perhpas the best way is to find test bench for it.

 

[Luchojry]

Problem is solved.
EPC and LS pistons were worned. Reason for oil temperature was located on pilot pump. Pump was tested on test bench.
If someone have problems with these (Komatsu build) pumps, perhpas the best way is to find test bench for it.

Hello JTH! I have a bit same problem with you. Mine is i got no PC-EPC OUTPUT pressure it is zero. What EPC and LS piston are you referring to? Can i see? Thanks a lot.