Hydraulic Pump failure is easily confused with insufficient power of the main control valve,Pilot Pump,and engine.It is necessary to first investigate peripheral faults,measure system pressure,flow rate,and pump oil leakage,and then determine that the pump body is damaged and seize the opportunity for replacement.

　　Firstly,the overall movement of the machine is weak and the pressure is insufficient.The engine power is normal,but the excavation is sluggish and the heavy load pressure does not meet the standard;The refrigeration unit is still functioning properly,but the operation deteriorates significantly after heating up,indicating that the internal friction pair of the pump is worn and the internal leakage in the hot state has increased.

　　Secondly,hold the car and reduce the RPM.When performing composite actions or excavating loads,the engine speed drops significantly or even stalls.First,eliminate the engine malfunction,and then check if the hydraulic pump absorbs excessive power,the regulator is stuck,and the inclined plate cannot reduce the displacement,causing the engine to overload and stall.

　　Thirdly,there is abnormal noise and heating in the pump body.Continuous metal friction and impact noise occur at the position of the hydraulic pump;The temperature of the pump casing is abnormally hot,and the hydraulic oil temperature is rapidly increasing.

　　Fourthly,the return oil flow rate at the drain port is too high.At idle speed,the main pump's oil discharge pipe has a large oil output,far exceeding the standard leakage rate,indicating that the plunger and valve plate have been pulled and worn.

　　Fifth,the regulator is stuck and the action is disordered.The valve core of the regulator is stuck,which can result in either full opening with excessive flow causing blockage,or low flow causing slow operation of the entire machine.

　　Disassembly inspection:cylinder block and distribution plate are scratched and eroded;The plunger sliding shoe is worn and detached;The inclined plate is damaged;The regulator valve core is worn and stuck.If the above damage occurs,it is recommended to repair and verify or directly replace the assembly.

　　Be sure to first investigate the external causes:dirty hydraulic oil,filter failure,abnormal pilot pressure,and internal leakage of the main control valve.Do not change the main pump immediately upon seeing slow movement.After the hydraulic pump is damaged,there will be a large amount of metal debris in the hydraulic system.It is necessary to clean the oil tank pipeline and replace the complete set of hydraulic filter elements,otherwise the new pump will be quickly damaged by impurities.