Sunfire L4-138 2.3L DOHC VIN D MFI (1995)
Fuel Injector: Description and Operation
DESCRIPTION
The Multiport Fuel Injection (MFI) fuel injector assembly is a solenoid operated device, controlled by the Powertrain Control Module (PCM),
that meters pressurized fuel to a single engine cylinder. The PCM energizes the low impedance solenoid to open a normally closed ball valve. This
allows fuel to flow onto the top of the injector, past the ball valve, and through a recessed flow director plate at the injector outlet. The director
plate has machined holes that control the fuel flow, generating a conical spray pattern of finely atomized fuel at the injector tip. Fuel is directed at
the intake valve, causing it to become further atomized and vaporized before entering the combustion chamber.
An injector that is stuck partly open would cause loss of fuel pressure after engine shut down, so long cranking times would be noticed on some
engines. Dieseling could also occur because some fuel could be delivered to the engine after the ignition is turned "OFF."
