Diesel Injector Maintenance and Inspection Guidelines

The diesel injector is directly mounted on the cylinder head of a diesel engine, with its nozzle tip in contact with the high-temperature combustion chamber. Operating under extremely harsh conditions, it is one of the critical components affecting the diesel engine’s design performance and operational efficiency.

Compared with gasoline engines, diesel engines offer advantages such as higher thermal efficiency, better fuel economy, fewer faults, and lower exhaust emissions. In recent years, as drawbacks like low rotational speed, heavy weight, and high manufacturing/repair costs have been gradually overcome, diesel engines have been widely adopted.

During injector pressure adjustment, if oil dripping occurs or leakage is detected during the pressure-holding test, it indicates poor sealing of the needle valve assembly, requiring lapping of the mating parts.

Among the three precision assemblies in the diesel fuel system, the injector needle valve assembly exhibits the lowest operational reliability and shortest average service life. Common damages from prolonged use include: weakened injector springs; excessive wear of moving parts (especially poor sealing between the needle valve and valve body); carbon deposits blocking or reducing nozzle holes; and needle valve seizing. Inspection and identification methods are as follows:

1. Injector Sealing Test

Conduct the test on an injector tester:

Pre-set the tester pressure to 23–24 MPa and adjust the injector pressure to 24–25 MPa.

When the tester pressure drops from 20 MPa to 18 MPa, the duration should be 9–21 seconds (minimum 5 seconds for continued use, per diesel generator manufacturer Dingbo Power standards).

Notes:

Ensure the tester meets technical requirements: the high-pressure oil circuit must be tight, and the tester’s outlet valve assembly must seal well. Bleed air from the oil circuit, block the high-pressure outlet connector, and continue pressurizing to 23–24 MPa. When the pressure drops from 20 MPa to 18 MPa, the duration should be no less than 3 minutes.

Perform at least two tests and take the average. The difference between consecutive test durations must not exceed 2 seconds for pintle/plate-type injectors or 3 seconds for multi-hole long-type injectors.

2. Injection Quality Inspection

At the specified injection pressure, verify that diesel atomization meets requirements:

Actuate the tester handle at a frequency of 60–80 times per minute. The injected diesel should atomize well, with uniform concentration and a conical spray pattern, free from oil droplet splashing.

Fuel cutoff must be sharp without dripping. After multiple injections, the area around the nozzle holes should remain dry or slightly moist.

Dingbo Power has advanced testing equipment, modern production technology, professional manufacturing technology, perfect quality management system, and strong technical research and development capabilities. It can provide 3kW～2500kW various specifications of ordinary, automatic, four protection, automatic switching, low noise and mobile generator sets, high quality and low energy consumption to meet the diverse power needs of customers, and can also meet users with different voltages and different frequencies. It is required to create a parallel power supply system for multiple units. If you are interested in our product or any question on generator, welcome to send email to [email protected].