Fuel Injector: Description and Operation

MFI Fuel Injector Assembly:

DESCRIPTION
The SFI fuel injector assembly is a solenoid operated device, controlled by the PCM, that meters pressurized fuel to a single engine cylinder.

OPERATION
The PCM energizes the low impedance (12.0 ohms) solenoid to open a normally closed ball valve. This allows fuel to flow into the top of the fuel 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.

A fuel injector that is stuck partly open or leaking would cause a loss of fuel pressure after engine shut down, so long crank times would be noticed on some engines. Dieseling also could occur because some fuel could be delivered to the engine after the ignition is turned to the Off position.