How to diagnose Hitachi ZAXIS120 excavator walking slowly？

How to diagnose Hitachi ZAXIS120 excavator walking slowly？

The reason why Hitachi ZAXIS120 excavator walks slowly is checked:

1. After inspection, the walking pilot pressure is normal; when changing the left and right running hoses at the top of the center joint, it is found that the left running is normal and the right running is slow, so the faults of the walking motor and the walking relief valve are ruled out.

2. Therefore, the cause of the failure can be determined in the No. 2 pump or the oil circuit and circuit that pulls the variable of the No. 2 pump. Check the primary and secondary pilot pressures of the flow control of the No. 2 pump in turn, and find that the primary pilot pressure is normal and the secondary pilot has no pressure. Because the pilot pressure of the flow control of No. 1 pump is normal, it is determined that the fault is in the signal pull valve. After inspection, it is found that the spool of the flow control valve of No. 2 pump in the signal control valve is stuck in the normally open position. After replacing the spool, the fault occurs. The phenomenon remains.

3. But at this time, the secondary pilot pressure oil drawn by the flow rate of the No. 2 pump has reached the SB port of the pump regulator, and the output oil pressure of the No. 2 pump is normal, and the material tray of the No. 2 pump has not been found to be stuck after manual adjustment. in the phenomenon. Because the oil enters the regulator from the sB oil port, it only passes through the flow of the No. 2 pump to pull the solenoid valve, so the valve was checked, but no fault was found.

4. The valve controls the needle angle control valve of the No. 2 pump through the signal of the main controller (Mc), so the signal source (computer board) is checked again, and it is found that a chip on the computer board has an obvious burning level Sadly, after the replacement, all the faults of the car disappeared.