Fuel Delivery and Air Induction: Description and Operation
Fuel System:
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.
The fuel system consists of three major sub-systems:
1. Fuel storage.
2. Fuel injectors and control system.
3. Fuel delivery and return.
FUEL STORAGE
The fuel storage system consists of a fuel tank, fill spout and filler cap. The fuel filler cap's primary function is as an evaporative emissions control device and is therefore covered in detail in EMISSION CONTROLS. The remaining components are covered in this section by name.
FUEL INJECTION AND CONTROL
FUEL INJECTORS
The injectors are solenoid operated shutoff valves designed to deliver fuel in an appropriate spray pattern to promote total fuel atomization in the intake air stream.
THE FUEL INJECTION CONTROL SYSTEM
The engine control module 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 engine control module varies the injectors "ON" time to adjust the amount of fuel delivered during each individual firing cycle.
For a more detailed description of the fuel injection system operation, refer to COMPUTERIZED ENGINE CONTROLS. For all fuel system mechanical component descriptions, refer to this section by component name.
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 the fuel delivery rail (in referance 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, a fuel pressure accumulator and a fuel pressure regulator.
The fuel return system recovers excess fuel vented by the fuel pressure regulator (mounted on the fuel rail) 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 and therefore is addressed, jointly with the fuel supply lines, under the heading of FUEL/VAPOR LINES.
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 addressed under the heading of FUEL/VAPOR LINES in this section. Also 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 covered in detail in EMISSION CONTROLS.