Fuel Injector: Description and Operation

Injector Operation.:

Injector Control.:

PURPOSE
The purpose of the fuel control system is to deliver the correct amount of fuel to the engine under all operating conditions. Fuel is delivered to the engine by individual fuel injectors mounted in the ports of the intake manifold.

The PCM controls the amount of fuel delivered by changing how long the injectors are turned "ON" and "OFF" every 360 degrees of crankshaft revolution. This is called Simultaneous Double Fire (SDF) injection.

The PCM uses one injector driver circuit to control the injectors. The current in this circuit is allowed to climb to a peak of eight amps, then is very quickly reduced to two amps to hold the injector open.

CIRCUIT OPERATION
The MFI injector assembly is a solenoid operated device, controlled by the PCM, that meters pressurized fuel to a single engine cylinder. The PCM energizes the low impedance (2.0 ohms) solenoid to open a normally closed ball valve.


FUEL CONTROL
As the PCM energizes the injectors, this allows fuel to flow into the top of the injector, past the ball valve, and through a recessed flow director plate at the injector outlet. The director place has six machined holes that control the fuel spray, generating a conical spray pattern of finely atomized fuel at the valve, causing it to become further atomized and vaporized before entering the combustion chamber.