Fuel Delivery and Air Induction: Description and Operation

PURPOSE
Fuel Delivery
The Electronic Fuel Injection (EFI) delivers precise air/fuel mixture to the engine at the proper time under all operating conditions. This results in optimum engine performance and lowest possible levels of unburned hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases.

Air Induction
Air induction systems work in conjunction with the EFI delivery system measuring air drawn into the engines intake system. Air cleaner assemblies with various sensors and switches are used to measure air temperature, transmitting signals to the Electronic Control Assembly (ECA). Vacuum motors control inlet air temperature for cold engine driveability.

CONSTRUCTION
Fuel Delivery system consists of:
- A high pressure electric fuel pump
- Fuel pressure regulator
- Fuel injectors
- Fuel pump switch (located in the Vane Air Flow Meter)
- Fuel pump relay
- Fuel tank
- Inertia switch
- Connecting lines.

Air Induction system consists of:
- Air cleaner assembly
- Air inlet tube(s) or fresh air tube
- Air outlet tube(s)
- Dry-type air filter element
- Crankcase ventilation filter
- Crankcase ventilation hose

Air induction systems regulating heated air flow, use the components listed in addition to the following:
- Heat shroud
- Temperature sensors
- Vacuum control systems
- Vacuum motor door

OPERATION

Fuel Delivery System Schematic:

Fuel Delivery
To maintain optimum exhaust emission control and engine performance, proper control of fuel pressure across the fuel injectors is maintained by a pressure regulator. Because fuel pressure is a constant when fuel demand is not, the system includes a fuel return line that allows excess fuel to flow back through the regulator to the fuel tank. The amount of fuel the injectors will spray under a particular operating condition is determined by the ECA. The ECA receives signals from sensors that monitor airflow to the engine, engine coolant temperature, engine vacuum conditions, oxygen content, etc.


Air Induction
The air inlet tube(s) directs air into a dry-type air filter element. A crankcase ventilation filter provides filtered air to the crankcase ventilation hose that directs air to the outlet tube(s). The air outlet tubes direct filtered air from the air cleaner to the throttle body. Some air induction systems draw air in from a cool air source only, while the rest regulate air inlet temperature by drawing air in from a cool air source as well as heated air from a heat shroud mounted on the exhaust manifold. Heated air flow is regulated by means of a door operated by a vacuum motor controlled by delay valves, temperature sensors and other vacuum control systems. All vary with each application and engine calibration.