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Analysis Scheme of Common Fault Causes of Excavators

  1. Why is it difficult to start the excavator in winter? It is not only determined by its technical conditions but also affected by the outside temperature. It is more difficult to start at a low temperature in winter, mainly due to the following reasons:


(1) In winter, the climate is cold, the ambient temperature is low, the viscosity of the oil increases, and the frictional resistance of various moving parts increases, which reduces the starting speed and makes it difficult to start.


(2) The capacity of the battery decreases as the temperature drops, which further reduces the starting speed.


(3) Due to the reduction of the starting speed, the leakage of compressed air increases, and the heat dissipation of the cylinder wall increases, which greatly reduces the temperature and pressure of the air at the end of compression, which increases the delay period of diesel ignition, and even cannot be burned in severe cases.


(4) The viscosity of diesel oil at low-temperature increases, which reduces the injection speed. In addition, the swirl velocity, temperature, and pressure of the air at the end of compression are relatively low, so the atomization quality of the diesel injected into the cylinder is poor, and it is difficult to quickly form a good quality with the air. The flammable gas will ignite and burn in time, or even fail to catch fire, resulting in difficulty in starting.




  1. What are the conditions for the good starting performance of the excavator?


(1) There must be enough starting speed. The starting speed is high, the gas leakage in the cylinder is small, the heat transfer time of the compressed air to the cylinder wall is short, and the heat loss is small so that the gas temperature and pressure at the end of the compression can be improved.

(2) The tightness of the cylinder is better. This can further reduce the amount of air leakage, ensure that the gas has sufficient combustion temperature and pressure at the end of compression, and the compression pressure of the cylinder shall not be lower than 80% of the standard value.


(3) It is required that the matching clearance between the engine and the running parts is appropriate and well lubricated.


⑷ The battery must have sufficient starting capacity, and the technical condition of the starting circuit is normal.


⑸ The amount of starting oil meets the regulations, the injection quality is good, and the injection advance angle must meet the requirements.


⑹ Use fuel that meets the requirements.

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  1. When the excavator starts, the mechanical fault diagnosis and repair of the crankshaft cannot be rotated. When the engine is started, when the starting system is in good condition, press the start switch, the starter makes a noise and the crankshaft cannot rotate, which is a mechanical fault. The reasons why the crankshaft of the engine cannot be rotated are as follows.


(1) Poor meshing between the starter and the flywheel teeth. The ring gear and the starter gear will collide when starting the engine, causing damage to the teeth or single-sided wear of the teeth. If three or more teeth are continuously damaged or severely worn, it will be difficult for the starter gear to mesh with the ring gear teeth.


(2) Sticky cylinder. When the engine temperature is too high, the engine stops and stops, and the heat is difficult to dissipate. The piston ring and the cylinder adhere at high temperatures, and they cannot be started after cooling.


(3) The crankshaft is locked. Due to the failure of the lubrication system or the lack of oil, the dry friction of the sliding bearing causes the crankshaft to be locked and unable to start.


(4) The plunger of the fuel injection pump is stuck.


  1. The excavator can be rotated when it is started, but cannot be started (there is no smoke in the exhaust pipe). When starting the engine, there is no smoke from the exhaust pipe and no explosive sound, which is generally an oil circuit problem. The detailed analysis is as follows:


(1) There is no oil in the fuel tank.


(2) The fuel filter and oil-water separator are blocked.


(3) The low-pressure oil circuit does not supply oil.


(4) The fuel injection pump does not pump oil.


(5) There is air in the oil circuit.


(6) The gas distribution phase is out of alignment. The opening moment of the valve is not coordinated with the stroke of the piston in the cylinder. For example, when the piston makes a compression stroke in the cylinder, the intake and exhaust valves are opened, and the fresh air is driven out of the cylinder so that there is no combustion gas in the cylinder and it cannot be started.


(7) The solenoid valve of the fuel injection pump is broken and is in a closed state, and the diesel oil cannot enter the high-pressure chamber.


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