Fuel Injection System - Multi-Point: Description

The Multi-Point Electronic Fuel Injection (EFI) system is an electronically controlled system which combines electronic sequential fuel injection and electronic spark advance systems. Main sub-systems consist of: air induction, fuel delivery, fuel control, emission control, Electronic Control Unit (ECU), data sensors and switches.

Air induction system includes air cleaner, throttle body, Throttle Position Sensor (TPS) and the Idle Speed Stepper (ISS) motor.

Fuel delivery system provides fuel from fuel pump to the fuel control system. Fuel system is composed of an in-tank electric fuel pump, fuel filter and return line. Power is provided to operate fuel pump through a fuel pump relay located on right inner fender panel.

Fuel control system handles actual fuel delivery into the engine. Fuel pressure regulator maintains a constant fuel pressure of 31-39 psi (2.1-2.7 kg/cm² ). In addition to the regulator, fuel system consists of the fuel rail and 4 fuel injectors. On MPI engine, ECU controls EGR/EVAP solenoid operation.

The ECU is a digital microprocessor computer. ECU receives input signals from various switches and sensors. ECU then computes fuel injector pulse width ("on" time), spark advance, ignition module dwell, idle speed, canister purge cycles, EGR flow and feedback control from this information.