B250 3/4 Ton Van V8-318 5.2L VIN T FI (1992)
Engine Control Module: Description and Operation
General Operation
OPERATION
As input signals to the engine controller change, the engine controller adjusts its response to the output devices. For example, the engine controller
must calculate a different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT). There are several different
modes of operation that determine how the engine controller responds to the various input signals.
OPEN AND CLOSED LOOP MODES OF OPERATION
Modes of Operation are of two different types. Open Loop and Closed Loop.
^
During Open Loop modes, the engine controller receives input signals and responds only according to preset engine controller programming.
Input from the oxygen (02) sensor is not monitored during Open Loop modes.
^
During Closed Loop modes, the engine controller will monitor the oxygen (02) sensor input. This input indicates to the engine controller
whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-i part fuel. By monitoring the
exhaust oxygen content through the 02 sensor, the engine controller can fine tune the injector pulse width. This is done to achieve optimum
fuel economy combined with low emission engine performance.
MODES OF OPERATION
The fuel injection system has the following modes of operation:
^
Ignition switch ON
^
Engine start-up (crank)
^
Engine warm-up
^
Idle
^
Cruise
^
Acceleration
^
Deceleration
^
Wide open throttle (WOT)
^
Ignition switch OFF
The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration, and wide open throttle modes are Open Loop modes.
The idle and cruise modes, (with the engine at operating temperature) are Closed Loop modes.
