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 PCM. See INJECTION TIMING  . Injectors are connected to 12 volts through ASD relay during start-up, and through charging system during engine operation.

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

With injector connected to a pressurized fuel supply, a fine mist will spray from injector nozzle into intake port. Injectors use an electromagnet and spring pressure to open or close fuel metering plunger. When connected to battery voltage, coil of wire in injector becomes an electromagnet. Magnetic field generated will overcome spring pressure and raise plunger off its seat. When injector circuit is opened by PCM, magnetic field collapses and spring pressure forces 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 injector is fixed and fuel flow rate constant, only control variable is amount of time injector is open. By controlling time injector is open, PCM can decrease pulse width for engine idle or it can increase pulse width at wide open throttle.