What are the common faults of rotor pumps?

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Rotor pumps are widely used in diesel engines due to their small size, high speed, light weight, uniform oil supply, and low noise. However, they also have drawbacks such as the tendency of the plunger to get stuck owing to their high precision. 　　1. Common fault symptoms 　　1) No fuel supply; the injector does not discharge fuel. 　　2) Unstable rotation speed, with the diesel engine shaking. 　　3) There is air in the pump. 　　4) Low fuel supply volume. 　　2. Cause analysis 　　1) The injector does not spray fuel. 　　① Low fuel injection pressure: Usually due to incorrect adjustment of the rotor pump or clogged injection holes. 　　②Low fuel supply pressure: In most cases, this is caused by severe wear of the plunger or failure of the fuel pump, blockages in the low-pressure fuel circuit, or an empty fuel tank. If the high-pressure oil pipe is tightened too much, torque is stored. When the diesel engine is in operation, rising temperatures or vibrations cause this torque to be released, resulting in the oil outlet valve loosening, which can also lead to a decrease in oil pressure. 2) Unstable rotation speed 　　① Diesel engines equipped with rotor pumps generally have a relatively stable rotation speed; in case of abnormal behavior, it is necessary to check whether the injector is malfunctioning, and then verify whether the oil outlet valve seat of a particular cylinder is loose. 　　②An excessively low idle speed can also cause vibration in diesel engines; air in the diesel or a faulty fuel delivery valve can likewise lead to unstable engine speed. 　　3) Air in the pump 　　① Air in the low-pressure oil circuit. 　　②The drive shaft oil seal has failed. 　　4) Low fuel supply volume 　　① Improper adjustment: After working for a while, new plungers tend to fail relatively quickly; therefore, the fuel supply volume of the fuel injection pump equipped with new plungers should be increased by 0.5 min/100 cycles during calibration. 　　②Plunger wear: Severe plunger wear is characterized by the absence of an idle speed, no reduction in speed at high speeds, and the need to pull the shutdown lever in order to reduce speed; this is commonly known as false idling. 　　3. Fault Examples 　　Air in the rotor pump is a typical fault of the pump. The low-pressure oil circuit was found to be in good condition, but air was always present in the diesel engine after it had been running for a while. On several occasions, after the vehicle had traveled about ten kilometers, air suddenly forced all the oil out of the pump. Then the oil was pumped in, and after traveling about ten kilometers, this issue occurred again. Raising the fuel tank didn’t help, nor did using an electric fuel transfer pump. Upon further analysis, it was determined that the gas from the crankcase had rushed in through the oil seal on the drive shaft of the fuel injection pump; normal operation was restored after replacing the oil seal. 　　Additionally, the acceleration lever is a part of the pump that wears out easily, and oil leakage often occurs due to wear in this area. 　　Pumps are quite precise and have high requirements regarding the quality of the oil. Therefore, to extend the service life of rotary pump and fuel injection pumps, it is necessary to use diesel that has been settled and is of good quality.