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The injection pressure of the injector will be affected by many factors, as follows:
Fuel system pressure: The overall pressure of the fuel system is the direct factor affecting the injection pressure of the injector. The pressure provided by the high-pressure fuel pump is transmitted to the injector through the fuel pipeline. If the output pressure of the fuel pump is insufficient or there are problems such as leakage or blockage in the pipeline, the fuel pressure at the inlet of the injector will be reduced, which will lead to a decrease in injection pressure. Conversely, if the fuel system pressure is too high, the injection pressure of the injector will also increase accordingly.

Injector spring stiffness and preload: The spring stiffness and preload inside the injector determine the resistance of the needle valve to open. The greater the spring stiffness and the greater the preload, the greater the force required to overcome the needle valve to open, and the higher the injection pressure; conversely, if the spring stiffness becomes smaller or the preload is insufficient, the needle valve will be easier to open and the injection pressure will be reduced. After long-term use, the spring may become less elastic due to fatigue, resulting in changes in injection pressure.

Nozzle structural parameters: The nozzle's nozzle diameter, length, and number of structural parameters have an important impact on the injection pressure. The smaller the nozzle diameter, the greater the resistance to the fuel passing through, and the higher the injection pressure; the longer the nozzle length, the greater the friction resistance of the fuel flow, which will also increase the injection pressure. In addition, with the increase in the number of nozzles, the injection pressure of each nozzle may decrease at the same fuel flow rate because the fuel needs to be distributed to multiple nozzles.

Fuel quality and viscosity: The quality and viscosity of the fuel will affect its fluidity. If the fuel contains impurities, moisture, or high viscosity, it will increase the resistance to the flow of the fuel inside the injector, increasing the injection pressure. On the contrary, low-viscosity fuel has low flow resistance, which may cause a slight decrease in injection pressure. Different types and grades of fuel have different characteristics such as viscosity, which will also have different degrees of impact on the injection pressure.

Engine operating conditions: Changes in engine load, speed, and other operating conditions will affect the injection pressure of the injector. Under high load and high speed conditions, the engine needs more fuel to maintain power output. The fuel system will increase the fuel supply, and the injection pressure of the injector will also increase accordingly to ensure that the fuel can be fully atomized and well mixed with the air. Under low load and low speed conditions, the injection pressure will be relatively low.

Wear of the injector: After long-term use of the injector, the matching parts such as the needle valve and the valve seat, the plunger and the plunger sleeve will wear. Wear will cause the matching clearance to increase, and the fuel leakage inside the injector will increase, which will reduce the actual amount of fuel sprayed and the injection pressure. At the same time, wear may also affect the closing performance of the needle valve, resulting in unstable injection pressure.