Electronic Fuel Injection Control

The fuel injection system can be broken down into three major sub-systems: the air induction system, fuel delivery system and the electronic control circuit. These three systems operate to provide the exact amount of fuel required for efficient combustion under all operating conditions.
The fuel delivery system consists of an electric pump, control relays, hoses and lines, pressure regulator, and solenoid operated fuel injectors. The electric pump maintains a constant supply of fuel to the injectors, and fuel pressure is maintained by a vacuum operated regulator. The six injectors, which are mounted in the intake manifold runners for each cylinder, simultaneously inject one half the amount of fuel required by the engine with each revolution. The injectors operate when energized by the ECU, with the actual amount of fuel delivered per revolution being determined by the amount of time that the injectors are held open.
The air induction system consists of precisely formed ducts, a throttle plate and an air flow meter. This system provides sufficient air flow for engine operation, allows air flow to be controlled, and provides means for the ECU to measure the amount of air entering the engine.
The ECU controls fuel pump operation and fuel injection duration based on engine and vehicle operating conditions. The ECU monitors intake air flow and temperature, coolant temperature, engine RPM, throttle position, manifold vacuum and exhaust gas oxygen content. The ECU uses this information to determine the ideal air/fuel ratio, computes the injection duration necessary to provide this air/fuel ratio and controls the injectors accordingly. In addition, the ECU controls current flow to the electric fuel pump through a group of relays, preventing the pump from running if the ignition is left on with the engine stopped.