Fuel Injector: Description and Operation

Fuel Rail (Delivery Pipe) And Injectors:

Typical Fuel Injector:

The fuel injectors, located on the intake manifold near the cylinder head, are electrically operated solenoid valves that open when energized. The injectors get battery power from the main relay when the ignition is in the either the "START" or "RUN" position, and are energized when the ECU completes the circuit to ground. Injection timing and duration is determined by the engine control unit. Injectors are energized either all at the same time once each crankshaft revolution (during cranking and cold engine operation), or in pairs (normal warm engine operation).

The injectors are constructed of stainless steel and high density plastic, to resist corrosion. They consist of a fuel inlet with filter screen, an electrical solenoid and connector, and a pintle valve and nozzle. Injectors are held in place by the fuel rail and sealed by an O-ring and insulator.

To calculate fuel injection quantity and timing, the ECU utilizes information from various input sensors, making adjustments needed to maintain good driveability, fuel economy and low emissions under the full range of operating conditions.

Input information is calculated from these devices:

^ Water thermosensor
^ Oxygen sensor
^ Airflow meter
^ Intake air thermosensor
^ Throttle sensor
^ Idle switch
^ Atmospheric pressure sensor
^ Distributor Ne and G signals
^ Stop light switch
^ Neutral and clutch switches
^ A/C switch
^ Inhibitor switch
^ Ignition switch ("START" position)