In a diesel engine, what is the purpose of the fuel injector?

The fuel injector's primary function in a diesel engine is to deliver fuel into the combustion chamber. This process is critical because the timing and quantity of fuel injected directly influence the efficiency, power output, and emissions of the engine. The fuel injector atomizes the fuel, allowing for a fine spray that facilitates thorough mixing with the air in the combustion chamber. This enhances combustion efficiency, leading to better engine performance and lower emissions.

The other options center around different functions that are not directly related to the primary role of the fuel injector. Engine speed control typically involves the throttle and engine management system rather than the injector itself. Monitoring engine temperature is handled by temperature sensors, and measuring exhaust emissions requires specialized sensors and equipment, not the injector. Thus, the choice that emphasizes the delivery of fuel to the combustion chamber accurately reflects the fundamental purpose of the fuel injector in a diesel engine.