Fuel Delivery and Air Induction: Description and Operation

GENERAL DESCRIPTION
The fuel injection system delivers a precise amount of highly atomized fuel to the intake system to ensure optimum performance and emissions compliance. This is a single-point throttle body fuel injection system.

The Fuel System consists of three major sub-systems:
^ The fuel storage system,
^ Fuel injector with the supporting fuel injection control system, and
^ The fuel delivery and return system.

FUEL STORAGE
The fuel storage system consists of a fuel tank, fill spout and filler cap.

FUEL INJECTION AND CONTROL
The injector is a solenoid operated valve designed to deliver fuel in an appropriate spray pattern to promote total fuel atomization in the intake air stream.

The fuel injection control system consists of the ECU (Electronic Control Unit) and all of the engine and operating condition sensors. Using the information from the sensors to determine the proper fuel amount and delivery time, the ECU varies the injector "ON" time to adjust the amount of fuel delivered.

For a more detailed description of the fuel injection system operation, refer to COMPUTERS AND CONTROL SYSTEMS.

FUEL DELIVERY AND RETURN
The fuel delivery system delivers fuel at a pressure and quantity high enough to allow the fuel regulator to maintain a constant fuel pressure (in reference to the intake manifold pressure) under all driving conditions. A check valve in the fuel pump holds pressure in the system after engine shutdown to prevent vapor lock and to ensure adequate pressure is available during warm engine re-start conditions.

The fuel delivery components consist of fuel supply lines, a high pressure fuel pump (mounted in the fuel tank), a fuel filter assembly and a fuel pressure regulator.

The fuel return system recovers excess fuel vented by the fuel pressure regulator (mounted on the throttle chamber) and returns it to the fuel tank. The fuel return line is low pressure and returns directly to the fuel tank. The fuel return system consist of lines and couplings

FUEL VAPOR RECOVERY
The fuel vapor recovery system provides a route for the recovery of fuel vapors (from the fuel tank) either for storage in the charcoal canister, or for evacuation through the purge control system. The vapor recovery system also consists of lines and couplings. Additionally contained in the vapor recovery system are two components, an overfill limiter and a fuel check valve. These components function as evaporative emissions control devices and are therefore covered in detail in EMISSION CONTROL DEVICES.