Fuel Injection System - TBI: Description

Chrysler Throttle Body Fuel Injection system is a computer controlled system which uses a throttle-body assembly with a single fuel injector to control air/fuel ratio under varying engine operating conditions.

Fuel is supplied to engine through an electronically controlled (pulsed) injector valve located in the throttle body assembly on top of intake manifold. Power to injector is supplied by power module while length of time that injector is left open is the responsibility of logic module.

Logic module determines amount of fuel to be metered through injector valve based on engine operating condition information supplied to it by various engine sensors and switches. Input signals from these sensors/switches are converted, by logic module, into control signals.

These control signals are then sent to the power module which responds by issuing electrical signals to specific components to alter air/fuel ratio and/or ignition timing to meet indicated conditions. Logic module is a digital, pre-programmed computer which controls ignition timing, emission control devices and idle speed in addition to air/fuel ratio.

Fig 1: Schematic Diagram of Power/Logic Module Input Signals & Output Controls