1. Engine speed decrease
First, test the output power of the engine itself. If the output power of the engine is lower than the rated power, the causes of the fault may be poor fuel quality, low fuel pressure, wrong valve clearance, non operation of a cylinder of the engine, wrong fuel injection timing, wrong setting value of fuel quantity, air leakage of the intake system, defects of the brake and its control lever and carbon deposition of the turbocharger.
If the engine output power is normal, you need to check whether the flow of the hydraulic pump does not match the output power of the engine. In the operation of hydraulic excavator, the speed is inversely proportional to the load, that is, the product of flow and pump output pressure is an invariant, and the pump output power is constant or approximately constant.
If the pump control system fails, the load optimal matching state of engine, pump and valve in different working conditions can not be realized, and the excavator will not work normally. Such faults should start with the electrical system, then check the hydraulic system, and finally check the mechanical transmission system.
2. Slow down
The main reason for the slow working speed of the excavator is the wear of all parts of the whole machine, resulting in the decline of engine power and internal leakage of hydraulic system. The hydraulic pump of the excavator is a plunger variable displacement pump. After working for a certain time, the hydraulic components inside the pump (cylinder block, plunger, port plate, nine orifice plate, turtle back, etc.) will inevitably be excessively worn, which will cause internal leakage and uncoordinated parameter data, resulting in insufficient flow, excessive oil temperature and slow working speed. At this time, it is necessary to overhaul the whole machine and repair and replace the worn out parts.
However, if the excavator that has not worked for a long time suddenly moves slowly, it is necessary to check the following aspects.
First check whether the circuit fuse is open or short circuited, then check whether the pilot pressure is normal, and then check whether the servo control valve servo piston is stuck and whether the distributor confluence is faulty. Finally, disassemble the hydraulic pump for data measurement to confirm the problem of the excavator.
