Fuel Injection System - Multi-Point: Description
The 3.0L engine with Multi-Point Fuel Injection is used on the 1987 Caravan, Mini Ram Van and Voyager. A new design Single Module Engine Controller (SMEC) is the "brain" of the system. This system combines the Power module and the Logic module in one unit. The SMEC processes all sensor inputs and assigns control signals to all output devices to control injector pulse width ("on-off" time), spark advance, idle speed, and other engine functions.
In order to control these systems, the computer monitors several engine and vehicle operating conditions. Engine speed and manifold absolute pressure are the primary signals used to control the injection signal.
Injectors are mounted in each branch of the intake manifold and spray fuel directly into each intake port. The throttle body includes an air by-pass automatic idle system, operated by a stepper motor.
The SMEC tests many of its own input and output circuits. If a fault is found in a major circuit, a memory code is stored in the system. These codes may be accessed using diagnostic readout equipment or through the instrument panel power loss light. For further information on this system, see COMPUTERIZED ENGINE CONTROLS section.