Since the reform and opening up, China's economy has developed rapidly, various infrastructures are increasing, and the demand for various construction machinery vehicles is increasing, especially bulldozers.

　　The bulldozer not only improves production efficiency, but also saves manpower and financial resources. However, many construction units neglected the repair and maintenance of bulldozers, resulting in machine damage in many projects during the construction phase. The most common failure of bulldozers is engine failure. Here are some common failures and maintenance countermeasures of bulldozer engines for your reference!

　　1: Working principle of bulldozer engine

　　The bulldozer engine system is composed of hydraulic oil supply pump, high pressure oil pump, fuel injector, engine control module, sensor, instrument display system, etc. The hydraulic oil supply pump is responsible for providing driving pressure, the high-pressure oil pump is responsible for pressurizing the oil, the fuel injector is responsible for fuel injection, the control module is responsible for controlling the transmission signal, the sensor is used to sense the pressure of the pump, and the instrument is responsible for displaying the system values and reporting errors. The oil supply pump provides the driving pressure for the fuel injector. The oil pressure is increased to 21.5~50 MPa by the high pressure oil pump, and the fuel injector starts to work. During the working process, the generated signal is controlled by the control module to effectively adjust the pressure, and at the same time it can adjust its speed, control fuel, timing and other functions. The signal in the sensor is read through the Carter data line, and the Carter data line is connected to the instrument display system. The role of the throttle sensor is to allow the driver to control the speed of the bulldozer engine. In order to quickly raise the engine before the oil pressure accelerates the engine, during the process of starting the engine, it usually runs at idle speed for 2 seconds. The advantage of EMC support is that the speed/timing sensor is equipped with a main sensor, which can effectively detect the engine speed and timing; the secondary sensor, which can accurately identify the cylinder. It can also effectively avoid the wear of the traditional connecting rod system without connecting the machinery such as speed control and governor.

　　2: The main failure of the bulldozer engine

　　(1) Idle speed failure. During the operation of the bulldozer, it is sometimes found that the bulldozer engine has no idling speed.As long as the throttle is in the idle position, the engine will be turned off. When the throttle is continuously increased, the rotation and lifting are particularly fast.The bulldozer cannot run at a low speed; on the contrary, sometimes It was found that the bulldozer engine idling speed was too high during the operation of the bulldozer. When the oil was not supplied, the engine speed of the bulldozer was still extremely fast.

　　(2) Code failure. The bulldozer engine does not work, the instrument panel displays a fault code, and MID, CID, FID and other fault codes appear, indicating that the bulldozer engine has a fault.

　　(3) Engine start failure. After the machine is running, the starter motor works normally, and the oil supply circuit works normally, but the starter engine is always idling, the gasoline does not burn, and no smoke is removed through the smoke exhaust line.

　　(4) Insufficient power failure. The radiator of the motor oil is running normally, and the oil circuit is also working normally, but the bulldozer has been emitting black smoke. The analysis is the cause of insufficient power.

　　(5) Abnormal noise of operation. In the process of bulldozer work, there are always different levels of audible noise.

　　3: Countermeasures for maintenance of bulldozer engine

　　For the above faults, introduced the causes of the faults and solutions.

　　(1) Idle speed failure. No idle speed failure: The reasons for no idle speed failure are as follows: the spring installed on the governor breaks or does not work because its material is too soft, then the spring on the governor needs to be replaced; installed on the governor The sensor has caused a lot of wear due to long-term work. At this time, it is also necessary to remove the original sensor and replace it with a new sensor; the plunger of the fuel injection pump is seriously worn. The plunger of the fuel injection pump is worn due to long-term use, the solution is the same as above, and new parts need to be replaced; when the temperature is too low at start-up, the temperature is too low, the viscosity of the engine oil increases greatly, the engine running resistance increases, the evaporation and spray of the engine oil The condition becomes worse and the engine is not running smoothly. At this time, lifting the throttle will cause the engine to quickly shut down. The solution is to increase the rotation speed above idle speed, increase the temperature of the whole machine, reduce the viscosity of the engine oil, and reduce the running resistance of the engine. When the temperature rises, then return to idle speed operation.

　　Over-idle fault: The cause of over-idle is improper adjustment of the throttle operating lever. At this time, the throttle operating lever needs to be adjusted to make it in the proper position; the spring installed at the throttle return position is too soft to work, at this time It is necessary to replace the spring with greater hardness; the idle speed adjustment screw or the limit block fails, the solution is to carefully check whether the idle speed limit block is in the proper position or does not play a limit role due to wear and other reasons, carefully check whether the adjustment screw is adjusted properly, If gaps and other problems occur, the adjustment screw should be adjusted in time.

　　(2) Code failure. Code failure is the most direct detection of bulldozer engine failure, and is the first indicator to be considered after a failure. Therefore, familiar with the failure category of the operating instructions, you can quickly solve the code failure. When a code failure occurs on the instrument panel, you can find the cause and solution of the failure according to the failure category in the manual.

　　(3) Engine start failure. Use the EI monitor to monitor the oil pressure during driving to see if there is any abnormality. When the oil pressure is abnormal, consider whether there is a problem with the fuel injector. If the fuel injector has not been replaced for a long time, you need to replace it with a new one. After the replacement, check to see if it is operating normally. If the operation is still abnormal after the replacement, consider whether there is a leak during the installation process, such as sealing, install carefully After that everything will work fine.

　　(4) Insufficient power failure. Check whether the engine cylinder liner is corroded, whether it causes oil to leak into the water tank. When there is a leak, the fuel cannot be fully burned, which will cause insufficient power failure. The solution is to replace the new cylinder liner and piston and other parts; at the same time, check the cam height and camshaft to see if there is wear. When the wear is serious, it will cause insufficient combustion and cause black smoke. The solution is Replace parts.

　　(5) Abnormal noise of operation. First, remove the engine and check to see if there are any abnormalities in the parts, such as IV cylinder connecting rod bolts. When there is a large deformation, it will cause abnormal engine operation. The solution is to replace the connecting rod of the IV cylinder, or to replace the original connecting rod of the IV cylinder with better quality materials, so as to achieve the effect of curing both the symptoms and the symptoms.

　　4: Conclusion

　　In summary, when operating the bulldozer, you must fully understand it, not only to understand the working principle of the bulldozer engine, but also to bear in mind the possible faults, and regularly carry out maintenance and repair of the bulldozer engine. We must be strict and careful, and we should not pass by because there are no problems. Only by achieving the above points can the normal operation of the bulldozer engine be guaranteed and its efficiency be improved.