What parts make up the fuel injection system?

Answer 1

Fuel travels from the fuel tank, through the fuel filter, propelled by the fuel pump. The Engine Control Module (aka the ECM or computer) controls the fuel pump through a relay; basically it provides a signal at the time the key is turned on to run the pump for a few seconds to generate pressure, and then turns the pump on when it detects the engine is running.

After the fuel filter, fuel enters the fuel rail(s) in which are mounted fuel injectors. The injectors are basically solenoids or electrically controlled valves. When signaled by the ECM they spray a measured amount of fuel into the intake manifold just before the mixture enters the combustion chamber.

Auxiliary to the fuel injection system are several sensors which the ECM takes into account to vary the pulse width delivered to the injectors, adding more or less fuel into the combustion mixture. Among these sensors are mass air flow or manifold air pressure sensors (either of which determines the amount of air flowing into the engine through the intake), intake air temperature sensor, engine coolant temperature sensor (to alter the mixture to help the car warm up more quickly), oxygen sensors (to determine whether the mixture burned completely -- was the mixture rich or lean).