Electronic Fuel Injection

Fig. 1 Electronic fuel injection system:

The electronic fuel injection system, Fig. 1, consists of three basic systems. The fuel system consists of an electric fuel pump that supplies fuel under constant pressure to the injectors. The injectors operate simultaneously admitting one half the necessary amount of fuel into the intake manifold during each engine cycle. The air induction system provides the proper amount of filtered air for proper engine operation. The electronic control system consists of an EFI computer that receives input signals from various engine sensors. Information on changing engine operating conditions is supplied to the computer by sensors that monitor intake air volume and temperature, coolant temperature, engine load, throttle position and exhaust gas oxygen content. The computer uses this information to determine the injection duration necessary to provide the optimum air/fuel ratio.

Fig. 2 EFI System Schematic:

SELF DIAGNOSIS SYSTEM

By analyzing current flow through the electronic control circuits, the EFI computer detects malfunctions or abnormalities of the system sensors and actuators. When the computer detects a malfunction, it energizes a ``Check Engine'' lamp on the instrument panel and a malfunction or diagnostic code is stored in the computer memory. The warning lamp remains illuminated only as long as the malfunction continues, and is turned off once the malfunction has been corrected. However, the diagnostic code remains stored in the computer memory as long as battery voltage is supplied to the computer, and codes pertaining to both existing and intermittent malfunctions can be accessed for system service and during system diagnosis.