What are the reasons for the inability of the excavator to work properly?

1、 The control pressure output by the pressure reducing valve is too low


Under normal circumstances, the maintenance pressure reducing valve of a mountain excavator can reduce and stabilize the output oil pressure of the main pump at 3.3MPa, forming a control oil pressure. If the conical valve core on the pressure reducing valve is not tightly closed due to the dirty oil quality, it will cause the output pressure of the pressure reducing valve to be lower than 3.3MPa. At this point, no matter how the operating handle is activated, the control oil pressure is always low, and the movement of the valve core of the main control valve of various working devices is too small, resulting in a small flow rate to the working device, causing the entire machine to be weak.



2、 The overflow pressure of the main overflow valve is low


The main relief valve limits the high pressure of the entire hydraulic system to 32.5MPa. For high pressures exceeding this value, the main relief valve will open to relieve pressure to protect the system from damage. If the small hole on the main overflow valve core of a large excavator is blocked due to poor oil quality, resulting in the valve core being constantly open, or the set overflow pressure of the main overflow valve being too low, it will cause the actual overflow pressure to be too low, that is, the system pressure to be too low.



3、 The main pump output flow control valve group is faulty


The output flow rate of the main pump of the machine varies with the change of engine power, assuming that the power of the main pump and the engine are optimally matched and fully utilized. If there is a malfunction in the control valve group used to regulate the output flow of the main pump, such as a blockage in the PLS feedback circuit, a stuck LS valve core, a stuck PC valve core, or a burnt internal coil of the PC-EPC solenoid valve, it will cause the main pump to remain in a constant flow state. If the main pump remains in a low flow state, the machine will become weak and slow during operation.


Similarly, if the swashplate, servo piston, and other components of the main pump that directly control the flow change of the main pump are stuck, then the output flow of the main pump will not change.



4、 LS bypass valve faulty


The LS bypass valve can leak a portion of P15 pressure oil on the LS circuit through two small holes (slight) in the valve body to increase the softness of machine operation. If the O-ring seal on the valve body is damaged, the PL5 pressure oil will directly communicate with the oil tank, indirectly causing the unloading valve to open normally, causing weak and slow operation of various working devices.



5、 The unloading valve is faulty


When the driver starts the engine and places the lever in neutral, the main pump outputs hydraulic oil directly back to the fuel tank through the unloading valve, with a unloading pressure of 3MPa. If the unloading valve core is not tightly closed due to the dirty oil quality, the output oil of the main pump will pass through the unloading valve directly to the oil tank during machine operation, causing the system to fail to establish high pressure; Similarly, if the 0-shaped sealing ring on the unloading valve used to block the connection between PlS pressure oil and the oil tank is damaged, it will also cause the main pump hydraulic oil to directly flow back to the oil tank.