1. Failure of oil suction valve.
2. Pilot valve failure.
1. Check whether there is air in the system. If there is air, exhaust it.
Check whether the oil suction filter is blocked, and replace the filter if it is blocked.
Check whether the pump outlet pipe is unobstructed.
4. Low traveling pilot oil pressure: check the traveling pilot pressure, unscrew the screw plug above the traveling pressure switch connector, connect the pressure gauge at 60bar, and operate the traveling pilot handle (push to the bottom should be greater than 30bar, and some push should be around 18bar);Abnormal inspection or replacement of the pilot valve, mainly: stroke is not enough (adjustment), pressure regulating spring is too soft (replacement), stem stuck or wear (clearance of blockage or maintenance, replacement).
5. Check the leakage of the central rotary joint: disassemble the two high-pressure pipe joints on the left (right) side and plug up the plug, operate the walking joysstick. If there is a large amount of oil flowing out of the two oil ports of the rotary joint, it means the leakage is serious, repair and replace the seal (or rotary joint), and proceed to the next step normally.
6. Incomplete brake relief: The main reasons for incomplete brake relief are as follows: A brake pilot valve is stuck by foreign matter (removal);B. Brake cylinder oil seal is damaged and leaking (replace the seal);C, the balancing valve to the brake pilot valve is blocked (cleared).If normal, motor bearings or deceleration mechanism may be stuck, check and remove foreign matter.