Fault Modes of Diesel Engine Mechanical Fuel Injection System 3

The previous article introduced the main factors that cause failures in diesel generators, and in this article, we will continue to explain them.

(2) Changes in fuel injection pressure. During the operation of a diesel engine, the injection pressure often changes, causing the injection pressure to be either too high or too low. Excessive fuel injection pressure can cause early wear of the fuel injection pump plunger components and injectors, and sometimes even cause high-pressure oil pipes to expand and crack, resulting in cylinder knocking during diesel generator operation; If the fuel injection pressure is too low, it will cause poor fuel atomization, and the nozzle is prone to carbon buildup, making it difficult to start. The main reason for the change in fuel injection pressure is that the elasticity of the pressure regulating spring decreases or breaks, causing a decrease in fuel injection pressure; Excessive clearance between the needle valve guide part and the needle valve body, or inadequate sealing of the needle valve cone surface, can also reduce the fuel injection pressure. When the needle valve gets stuck in the closed state or the nozzle is blocked, it will increase the fuel injection pressure.

(3) Change in fuel supply advance angle. The change in fuel injection advance angle directly affects combustion performance. Due to the complexity of measuring changes in fuel injection timing, it is usually necessary to measure the fuel injection timing. The fuel supply advance angle has a significant impact on the performance of diesel generators, mainly affecting fuel efficiency, pressure rise rate, and maximum combustion pressure. If the fuel supply advance angle is too large, the amount of fuel burned during the compression process will be increased. Not only will the compression negative work increase the fuel consumption rate and power decrease, but also if the fuel supply advance angle is too large, the ignition delay period will be longer, and the pressure increase rate and maximum combustion pressure will rapidly increase, resulting in rough operation. If the fuel supply advance angle is too small, the fuel cannot burn quickly near the top dead center, and the afterburning increases. Although the maximum combustion pressure is low, the fuel consumption rate and exhaust temperature increase, causing the diesel engine to overheat.

So for each operating condition, there is an optimal fuel supply advance angle, at which point the fuel consumption rate is the lowest. During the use of diesel generators, there is often a change in the fuel supply advance angle, mainly due to: 1. The fixing bolts of the connecting plate of the fuel injection pump coupling are loose and displaced, causing the fuel supply advance angle of each cylinder to be delayed; 2. The adjustment bolt on the roller strut of the fuel injection pump is loose, causing a change in the advance angle of individual cylinder fuel supply; 3. Individual fuel injector needle valves are not tightly closed or the injection pressure is reduced, as well as the fuel outlet valve is not tightly closed, causing the advance angle of individual cylinder fuel injection to advance; 4. When the fuel injection pressure is adjusted too high, it will reduce the advance angle; 5. The wear of the fuel injection pump roller follower, oil pump cam, plunger and sleeve will reduce the fuel supply advance angle.

(4) Low pressure oil circuit blockage or air leakage. Blockages or leaks in low-pressure fuel circuits can cause insufficient power or difficulty starting diesel engines. This is mainly because the blockage of the oil circuit or the entry of air will greatly reduce the effective fuel flow, leading to insufficient power or difficult starting faults in the diesel engine due to insufficient fuel supply.

From this, it can be seen that the wear of precision components of the plunger/outlet valve/injector needle valve, changes in fuel injection pressure, changes in fuel supply advance angle, and blockage or leakage of low-pressure oil circuits are the main causes of mechanical fuel injection system failures in diesel engines. We hope this can be helpful to everyone.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.