In a diesel fuel system, what is the primary function of the fuel injector?

The primary function of a fuel injector in a diesel fuel system is to deliver a precise amount of fuel, at a precisely controlled timing, directly into the engine's combustion chamber in a highly atomized spray. Atomization refers to breaking the fuel into very fine droplets, which increases its surface area and allows it to mix more effectively with the compressed air in the cylinder. Diesel engines use compression ignition, meaning that the heat generated by compressing the air in the cylinder ignites the fuel. The fuel injector must deliver the fuel at the correct moment in the engine's cycle to ensure efficient combustion. The timing and quantity of fuel injected are controlled by the engine control unit (ECU), which uses sensor data to optimize engine performance, fuel efficiency, and emissions. Modern diesel fuel injectors are electronically controlled and can perform multiple injections per combustion cycle, such as pilot injection to reduce engine noise and improve cold starting, and main injection for power. The high-pressure fuel is forced through a small nozzle in the injector, creating the fine spray. A malfunctioning fuel injector can cause a variety of problems, including reduced power, poor fuel economy, excessive smoke, and engine knocking. For example, a diesel fuel injector that is not atomizing the fuel properly will result in incomplete combustion and increased emissions.