Cherokee 2WD L4-150 2.5L VIN P MFI (1991)
Fuel Injector: Description and Operation
Fuel Injector - Cutaway View
The fuel injectors are solenoid operated valves that deliver fuel, in a metered amount, to the combustion chambers of individual cylinders. When the
solenoid coil is energized, the plunger is retracted lifting the needle valve off its seat, allowing fuel to be injected into the combustion chamber. When
the solenoid is de-energized spring pressure closes the valve.
The system fuel pressure is maintained, by the fuel pressure regulator, at 31 psi with vacuum applied to the fuel pressure regulator. The fuel pressure
will increase by 8 to 10 psi if no vacuum is applied at the fuel pressure regulator. The amount of fuel that is injected is determined by the amount of time
that the needle valve remains open. This time is commonly referred to as the "pulse width" of the injector. The SBEC II controls the pulse width of the
injector to change the air/fuel ratio for varying engine driveability conditions.
The fuel injector wiring harness has a tag that is attached to each injector connector, the tag has its respective cylinder number attached to it for ease of
identification.
