B250 3/4 Ton Van V8-318 5.2L VIN T FI (1992)
Engine Control Module: Description and Operation
Modes of Operation
Ignition Switch On
This is an Open Loop mode. When the MPI system is activated by the ignition switch, the following actions occur:
^
The engine controller pre-positions the automatic idle speed (AIS) motor.
^
The engine controller determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy.
^
The engine controller monitors the coolant temperature sensor input. The engine controller modifies fuel strategy based on this input.
^
Charge Air Temperature sensor input is monitored
^
Throttle position sensor (TPS) is monitored
^
The auto shutdown (ASD) relay is energized by the engine controller for approximately three seconds.
^
The fuel pump is energized through the fuel pump relay by the engine controller. The fuel pump will operate for approximately one second
unless the engine is operating or the starter motor is engaged.
^
The O2 sensor heater element is energized through the fuel pump relay. The O2 input is not used by the engine controller to calibrate air-fuel
ratio during this mode of operation.
Engine Start-Up
This is an Open Loop mode. The following actions occur when the starter motor is engaged.
The engine controller receives inputs from:
^
Battery voltage
^
Coolant temperature sensor
^
Crankshaft position sensor (CPS)
^
Charge Air Temperature sensor
^
Manifold absolute pressure (MAP) sensor
^
Throttle position sensor (TPS)
^
Starter motor relay
^
Sync signal (in the distributor)
The engine controller monitors the crankshaft position sensor (CPS). If the engine controller does not receive a CPS signal within 3 seconds of
cranking the engine, it will shut down the fuel injection system.
The fuel pump is activated by the engine controller through the fuel pump relay.
Voltage is applied to the fuel injectors with the engine controller. This controls the injection sequence and injector pulse width by turning the
ground circuit to each individual injector on and off.
The engine controller determines the proper ignition timing according to input received from the crankshaft position sensor (CPS).
Engine Warm-Up
This is an Open Loop mode. During engine warm-up the engine controller receives inputs from:
^
Battery voltage
^
Crankshaft position sensor (CPS)
