HI, Need help , MD120LC serial # 0472 ,service tech out all day testing machine for no hydraulics. Pilot pressure 700 at rack and back from controls, there is no oil coming back out of rack to signal pumps to start.Also tried connecting straight to servo from pilot pump still nothing. Filter clean,it had worked all day prior to end of day shut down . Any help would be great ,thanks
If you route the signal line to the pump's outlet does it run up to the cut off pressure?
Mike, Thank you for responding, the Kobelco tech left yesterday not knowing what to try next after hooking pilot line directly to servo for pump 2 and nothing happened. When you ask (If you route signal line to the pump's outlet does it run up to the cut off pressure) he did not try that,he's having a hard time not having the service manual for it, only newer models,then phone calls to others that may have worked on the older ones.Any pictures would be great as each picture is a thousand words and visual understanding.
Don't have any picture's. Just guessing that is load sensing... not flow sensing. So the pump sits at standby all the time.. say 3-400psi? And what do you have for pilot pressure at the spools? When you actuate a function is there any change in pressure on the smaller hoses running to the pump control?
Mike just e-mailed you my photos, we have good pressure at spools from controls but nothing leaving going to pump.I was working controls Kobelco tech at gage end he said one was lower at about 350# others closer to 700#
Mike ignore the arrows I stole the picture from another post
OK, Im taking it you mean you had 350-700 at the spools for your pilot pressure. Which should work. But what do you have between the outlet of the pump and the valve with no function activated compared to when it is activated? I would ask the same for the smaller lines that run from the valve to the control on the pump. What do you have with no functions activated compared to activated? It will take some time to learn the system without a manual but it can be done
The tests at spools were dead end test to make sure we had signals,never did test for pump pressure as the tech figured movement would tell if pump was working. We had no flow at all going from valves to pump servo( back to picture small line below A is going to pump ,behind A is line coming from pilot to check valve and flow reducer,behind B and lower out of sight is line coming from pilot for tracks which bypasses safety solenoid .Never checked any low pressure lines to see if we had flow just passing though