Fuel Injector: Description and Operation

MFI Fuel Injector:

PURPOSE
- The fuel injector nozzles are electro-mechanical devices that meter and atomize fuel delivered to the engine.

OPERATION
- The injector always opens the same distance, and the fuel pressure is maintained at a constant value by the pressure regulator. The amount of fuel delivered by the injector depends on the amount of time that the nozzle is open. This is the injector pulse width: The time in milliseconds the injector nozzle is open.

- An electrical signal from the Powertrain Control Module (PCM) activates the injector solenoid causing the pintle to move inward off the seat, allowing fuel to flow through the orifice. Atomization of the fuel is obtained by contouring the pintle at the point at where the fuel separates.

CONSTRUCTION
- This specialized solenoid has an armature and a needle or ball valve with a spring that holds the needle or ball closed against the valve seat. The armature opens the valve when it receives a current pulse from the PCM. When the solenoid is energized, it unseats the valve to inject fuel.