Electronic Fuel Injection -- Single Unit: Description
The General Motors single unit Electronic Fuel Injection (EFI) system consists of 7 major sub-assemblies: Fuel supply system, Throttle Body Injector (TBI) assembly, Idle Air Control (IAC) system, Electronic Control Module (ECM), Electronic Spark Timing (EST), data sensors and emission controls.
Fuel is supplied to engine through an electronically pulsed (timed) injector valve located in throttle body on top of intake manifold. The ECM controls amount of fuel metered through injector valve based upon engine demand and efficiency information. The ECM is a digital electronic computer which receives and computes signals from various data sensors.
NOTE:
Primary sub-systems which affect fuel system operation will be covered in this article: Fuel supply system, TBI assembly, IAC system, ECM and data sensors. Because of the interrelated functions of the Computer Command Control (CCC) system (the ECM is the "brain"), refer to "GENERAL MOTORS COMPUTER COMMAND SYSTEM" in Computerized Engine Controls section for more information.