Fuel Injection System - Multi-Point: Description
The AMC Multi-Point Electronic Fuel Injection system is an electronically controlled system which combines electronic fuel injection and electronic spark advance systems. The main sub-systems consist of: Air Induction, Fuel Delivery, Fuel Control, Emission Control, Electronic Control Unit (ECU) and Data Sensors.
The Air Induction system includes air cleaner, throttle body, Throttle Position Sensor (TPS) and the Idle Speed Stepper (ISS) motor.
The Fuel Delivery system provides fuel from the fuel pump to the fuel control system. It also returns excess fuel to the fuel tank. The system is composed of an in-tank electric fuel pump, fuel filter and return line. Power is provided to operate the fuel pump through a fuel pump relay located on the right inner fender panel.
The Fuel Control system handles the actual delivery of fuel into the engine. The fuel pressure regulator maintains a constant fuel pressure of 31-39 psi (2.1-2.7 kg/cm2 ). In addition to the regulator, the system consists of the fuel rail and 4 fuel injectors.
Emission systems controls, although directly operated by the ECU, are not unique to the Multi-Point EFI engine. Used on the MPI system is an ECU controlled EGR solenoid.
The ECU is a digital microprocessor computer. The ECU receives input signals from various switches and sensors. It then computes the fuel injector pulse width ("on" time), spark advance, ignition module dwell, idle speed, canister purge cycles, EGR flow and feedback control from this information.