MEFI Fuel Injection
MPFI Injector Fuel inlet filter
Upper O-ring
Solenoid windings Iron shuttle
Director plate
Core spring Pintle and seat
Lower O-ring
Spray tip
Conical spray
The injectors are supplied with 12 volts from the ignition/fuel relay. Drivers in the ECM supply a ground to the other terminal of the injector to actuate the solenoid. The ECM energizes the injector solenoid, which opens a ball valve allowing pressurized fuel to flow through a flow director plate that has a number (4-8) of machined holes creating a conical pattern of finely atomized fuel. The fuel is directed at the intake valve aiding in valve cooling and additional atomization. The multi-port system uses 2 injector drivers. The amount of fuel injected is determined by the length of time that the injector is energized, called Pulse Width. The unit of measure used for injector “on” time is milliseconds. Again, as with the TBI injectors, the pulse width is based on the fact that an injector discharges a known amount of fuel per millisecond at a specific fuel pressure and at a specific supply voltage, so maintaining proper pressure is ESSENTIAL to providing proper air/fuel ratio. When injectors stick or seize, no fault code will be set. Injector codes set for opens or shorts in the driver circuit back to the ECM.
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