What does a fuel injector do?

A fuel injector regulates the injection of fuel into an engine’s internal combustion chamber where it is mixed with air and ignited. The combustion chamber is where the chemical energy in diesel, hydrogen, and natural gas is converted into power for the vehicle. When actuated by the electronic control unit (ECU), the injector delivers a precise amount of fuel to ensure efficient combustion.

A fuel injector in a diesel engine consists of a solenoid (a type of electromagnet), a nozzle, and a needle within the injector body. Modern diesel engines are direct injection, meaning fuel is delivered directly into the combustion chamber.

In the cylinder, air is compressed by the upward movement of the piston. As the piston nears the top of its path, an electrical signal is sent to the solenoid, causing the injector needle to lift, and allowing high pressure fuel (up to 37,000 psi) to flow through the nozzle and into the combustion chamber to mix with air. Because of the elevated temperature created by the compression stroke, the air-fuel mixture auto-ignites, creating power and driving the engine's pistons.

The combination of high fuel pressure and exceptionally fine injector nozzle holes ensures optimal mixing of air and fuel to meet even stricter emissions standards. In diesel engines, a fuel injector can fire multiple pulses in a single power stroke which can be used for noise mitigation and emissions control.