General System Description

Fig. 1 Electronic control system operation:

Multi-port Fuel Injection (MFI) and Sequential Fuel Injection (SFI) provide a means of fuel metering which insures a precise air/fuel mixture and superior fuel distribution, resulting in reduced exhaust emissions and improved driveability under all driving conditions.
The MFI and SFI engines share many similar components. The main operating difference between two types of injection systems is in fuel delivery. The MFI engines inject metered fuel into all cylinder inlet ports at the same time once every engine revolution. Using this method two injections of fuel are required to produce the charge for each combustion cycle. The SFI engines inject metered fuel sequentially into each cylinder inlet port once per working cycle (every two revolutions) just prior to the opening of each intake valve.
An Electronic Control Module (ECM) is used to determine the amount of fuel delivered to the engine. The ECM receives signals from a variety of sensors and devices to know what mode of operation the engine is being subjected to, then analyzes the information and controls fuel delivery, ignition timing and a group of related components to ensure proper engine operation, Fig. 1. The constant measuring and adjusting of the air/fuel ratio, is known as ``Closed Loop'' operation.
The ECM is capable of diagnosing faults with the various inputs and systems it controls. When the ECM detects a malfunction, a ``Check Engine'' or ``Service Engine Soon'' lamp in the instrument panel is illuminated, warning the driver to have the system checked.
Fuel is supplied to the injector fuel rail by a tank mounted high pressure fuel pump. A pressure regulator is integral with the fuel rail to keep fuel available to the injectors at a constant pressure. The fuel pump is operated by the ECM through the fuel pump relay and oil pressure switch.