Fuel Injector: Description and Operation

Fig. 6 Fuel Injector Location Typical:

The injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port (Fig. 6).

Fig. 7 Fuel Injector Typical:

The fuel injectors are electrical solenoids (Fig. 7). The injector contains a pintle that closes off an orifice at the nozzle end. When electric current is supplied to the injector, the armature and needle move a short distance against a spring, allowing fuel to flow out the orifice. Because the fuel is under high pressure, a fine spray is developed in the shape of a hollow cone or two streams. The spraying action atomizes the fuel, adding it to the air entering the combustion chamber. Fuel injectors are not interchangeable between engines.

The PCM provides battery voltage to each injector through the ASD relay. Injector operation is controlled by a ground path provided for each injector by the PCM. Injector on-time (pulse-width) is variable, and is determined by the PCM processing all the data previously discussed to obtain the optimum injector pulse width for each operating condition. The pulse width is controlled by the duration of the ground path provided.

Fuel injectors are fired one crankshaft revolution before TDC compression. when cylinder #4 is at TDC compression the injector for cylinder #1 will be energized.