Have a SK120LC Mark III. Just replaced the pumps and pilot pump because of what was thought to be weakness (over 10,000 hours, and the tracks were getting slow). The new pumps fixed the tracks, but now there is other functions that are operating very sporadic and slow; the system seems to have a pilot pump dead head when the workload switch is in S mode. I don't have a diagram of the hydraulics and electrical for the workload switches and solenoids. Also there doesn't seem to be any voltage going to the solenoid on the regulator??? when should this solenoid be excited?? In H Mode the swing and the dipper arm are very slow, In S mode the bucket is very slow until under a load, There isn't a mode where everything works like it should, so I am lost now.
See attached schematic. A few questions, 1. Did the last pumps fail, or just wore out? 2. Did you clean the hydraulic tank/replace oil when new pumps were installed? Turn the pilot control pattern change lever (if equipped), and see if the problem follows the function, or the lever. The pf solenoid on the pumps should only have power when the computer wants to destroke the pumps. Check and see if you have a bad travel pressure switch, because if I remember right, the pumps get destroked some when the travel is engaged.
I thought that the pumps were weak...might not have been although they did get very hot (putting out a fire). The same problem exists even after new pumps, fluid, and filter. The sluggish operations seem to change depending on which workload setting the machine is on. When the machine is under a full load, it seems to operate better...like when just lowering the stick it seems like it falls under gravity and then once the hydraulics catch up with it then it takes of strong?? Can anyone tell me what the sequence of operations of the 3 solenoid valves under the cab are?? The diodes near these solenoids are letting small voltage back by them (2vdc) could this be a problem?
I thought that the pumps were weak...might not have been although they did get very hot (putting out a fire). The same problem exists even after new pumps, fluid, and filter. The sluggish operations seem to change depending on which workload setting the machine is on. When the machine is under a full load, it seems to operate better...like when just lowering the stick it seems like it falls under gravity and then once the hydraulics catch up with it then it takes of strong?? Can anyone tell me what the sequence of operations of the 3 solenoid valves under the cab are?? The diodes near these solenoids are letting small voltage back by them (2vdc) could this be a problem?
What is your serial number I may have a manual
Serial # YPO2039 this one was made at a CNH facility. I have a manual, but it doesn't reference the Variable loading mode??? Can you tell me where the pressure switch is located on the machine?
All I can do is look in the manuals that I have and try to find it. I am still in learning mode on these machines myself.
Did you every figure anything out? I just bought a 1993 Kobelco SK120 Mark III everything works but it slow until you use 2 functions like tracking and digging or digging and slightly engaging the tracks
I did figure out my problem I hired Mr. Kobelco and he helped a lot. my problem was a stuck valve on the independent travel solenoid next to the pump it wasnt the solenoid but the valve block itself.
Good day please see attached may be helpful. Kind regards Uffex