Electronic Fuel Injection (efi) is the name given to the entire fuel injection system. Various subsystems are combined to form the overall system. These subsystems are:
- Fuel supply system
- Throttle body assembly
- Idle control
- Idle Air Control (iac)-V6 engines
- Idle Speed Control (isc)-V8 engines
- Electronic Spark Timing (est)
- Emission controls
The fuel control system starts with the fuel in the fuel tank. An electric fuel pump, located in the fuel tank with the fuel gauge sending unit, pumps fuel to the fuel rail through an inline fuel filter. The pump is designed to provide fuel at a pressure above the pressure needed by the injectors. A pressure regulator in the fuel rail keeps fuel available to the injectors at a constant pressure. Unused fuel is returned to the fuel tank by a separate line.
The injectors are controlled by the ecm. They deliver fuel in one of several modes as previously described. In order to properly control the fuel supply, the fuel pump is operated by the ecm through the fuel pump relay and oil pressure switch.