Fuel Injectors

Fuel injectors are connected to a pressurized fuel rail and positioned in intake manifold above intake valves. Fuel injector wiring harness has a tag to identify each injector (INJ 1, INJ 2, etc.).

Injectors are energized individually in a sequential order controlled by the PCM. Injectors are connected to 12 volts through ASD relay during start-up and charging system during engine operation.

Injector is energized when connected to ground through the PCM. The PCM also controls the amount of time the injector is energized (pulse width) by turning ground on and off. Pulse width is based on various inputs and is calculated by the PCM.

With injector connected to a pressurized fuel supply, a fine mist will spray from the injector nozzle into the intake port. The injector uses an electromagnet and spring pressure to open or close the fuel metering plunger. When connected to battery voltage, the coil of wire in the injector becomes an electromagnet. The magnetic field generated will overcome spring pressure and raise the plunger off its seat. When the injector circuit is opened by the PCM, the magnetic field collapses and spring pressure forces the plunger against its seat.

Whenever an injector is opened, it will always spray a consistent amount of fuel for a given amount of pressure. Because pressure drop across the injector is fixed and the fuel flow rate constant, the only control variable is the amount of time injector is open. By controlling the time the injector is open (pulse width), the PCM can decrease pulse width for engine idle or it can increase pulse width at wide open throttle.