Fuel Injector: Description and Operation

Injector Schematic:

PURPOSE
The fuel injectors spray highly atomized fuel into the intake system to promote complete combustion of the air/fuel mixture.

LOCATION
Injectors are located along the edge of the intake manifold, near the cylinder head mating surface.

CONSTRUCTION
Each injector is constructed of a metal housing which contains a magnetic solenoid operated pintle. Fuel is sprayed through a nozzle to the intake port in the head. The injector inlet houses a fine mesh screen to filter out foreign particles. Top and bottom o-rings seal the outside of the injector to the intake manifold and fuel rail.


OPERATION
When the engine is cranking or running, constant voltage is supplied to the positive side. The ECM grounds the negative side of the solenoid valve, completing the electrical circuit, which energizes the magnetic winding. The magnetic field raises the injector pintle. When the pintle is raised, pressurized fuel sprays through a metered orifice into the intake system.

Injectors are triggered in 3 groups by the ECM. As system voltage lowers, more time is required to bring the injector from closed to open. The ECM monitors system voltage and corrects duration to compensate for delays caused by line voltage.