Fuel Systems: Gasoline Fuel Systems: EFI fuel supply system

Fuel pumps	EFI fuel pumps operate electrically to provide fuel under pressure to the fuel rail and the injectors.
Fuel filters	EFI fuel filters remove contaminants from the fuel, so that clean fuel can be supplied to the injectors.
Tanks & lines	Most fuel tanks are in 2 parts joined by a weld around the flanges where the parts fit together. Baffles make the tank more rigid, prevent surging of fuel, and ensure fuel is available at the pickup-tube.
Fuel lines	The fuel tank is connected to the engine by fuel lines. A return line may carry excess fuel back to the tank, to keep fuel system components cool.
Fuel rail	The fuel rail supplies fuel to the injectors under constant pressure.
Fuel pressure regulator	The fuel pressure regulator controls the return of fuel to the fuel tank, to maintain the pressure in the fuel rail at a constant value above intake manifold pressure.
Injectors	Injectors are solenoid-operated valves which deliver fuel in the form of an atomized spray, into the intake manifold, or the intake ports.
Tachometric relay	The tachometer indicates engine RPM.
Thermotime switch	The thermotime switch senses engine coolant temperature, to control the operation of the cold start injector, during cranking conditions.
EFI sensors	An oxygen sensor is positioned in the exhaust pipe, and provides the engine management ECU with an electrical signal that relates to the amount of oxygen in the exhaust gas.
Potentiometer	A potentiometer is a mechanically variable resistor.
Auxiliary air valves	Auxiliary air valves allow additional air to bypass the throttle plate during cold start, and warm-up conditions.
Idle speed control devices	Idle speed control devices allow the preset idling speed to be maintained automatically when additional loads are placed on the engine, during idling conditions.
Inertia sensors	Shut off the fuel pump(s) in case of an accident, preventing fuel from being continually pumped and spilled over the vehicle if there is a leak in the system.