The fuel injection system supplies the fuel necessary for combustion to the injectors at a constant pressure. Fuel is metered and injected into the intake manifold according to the injection control signals from the Engine Control Unit (ECU) or Engine Control Assembly (ECA). Most fuel injection systems consist of the following components: a fuel filter, distribution pipe, pulsation dampener, pressure regulator, injectors, fuel pump switch located in the airflow meter or mass airflow sensor for Navajo and the electric fuel pump usually located in the fuel tank in order to keep operating noise to a minimum.
The ECU or ECA, through various input sensors, monitors battery voltage, engine rpm, amount of air intake, cranking signals, intake temperature, coolant temperature, oxygen concentration in the exhaust gases, throttle opening, atmospheric or barometric pressure, gearshift position, clutch engagement, braking, power steering operation and air conditioner compressor operation.
The ECU or ECA controls operation of the fuel injection system, idle up system, fuel evaporation system and ignition timing. The control assembly has a built in fail safe mechanism. If a fault occurs while driving, the control assembly will substitute pre-programmed values. Driving performance will be affected but the vehicle will still, in most cases be drivable.