Fuel Injector: Description and Operation

Fuel Injector (Bosch):

Signal comes from the fuel injection ECU:

PURPOSE AND LOCATION
The fuel injectors (one per cylinder) are the main component of the fuel injection system. They supply the fuel which is injected in front of the intake valves. The injectors are positioned in the intake manifold.

CONSTRUCTION
The injectors consist of a fuel filter (screen), needle valve, solenoid, magnetic winding and the electrical connector for the ECU. The needle valve solenoid opens when the magnetic winding is energized and closes when without current.

OPERATION
The fuel injection ECU grounds the electrical circuit to operate the injectors. The injectors open and close simultaneously twice per revolution when the engine is starting (cold start) and once per revolution during normal engine operation.

The air/fuel mixture is controlled by the duration of the "open" (injector is energized) cycle which determines the amount of atomized fuel injected into the intake manifold.

SIGNAL
The injectors are supplied with current as soon as the ignition is turned "ON". The fuel injection ECU then controls the ground connection to operate the injectors.