I am new in construction/equipment business A have a excavator which model is Hitachi EX120-2 When i pull the hand pilot valve or travel pilot valve slowly then engine stalls easily but when i pull them very fast then engine ok and excavator works very fast and in this situation cant operate what can i do now?
Sounds like it could be a pump control issue or connectivity issue. The first thing I would do is check the hydraulic computer code output (the lower computer behind the seat). It has a red lens in the top rear center which will flash long for 10's and short for 1's. Read it several times to be sure you have the correct fault code(s), then write it (them) down. Causing the codes to display requires a jumper be installed in the test harness connector on the right side of the seat. The test manual will tell you what the codes say and how to install the jumper.