Fuel Injector: Description and Operation

PURPOSE
The fuel injectors are solenoid operated valves installed in the intake manifold. The fuel injectors spray a metered amount of highly atomized fuel into the engine intake system to maintain proper air/fuel ratio and promote efficient combustion.

OPERATION
The injector is a solenoid actuated, constant stroke, pintle type. Components include a solenoid, plunger needle valve, and housing. When the solenoid coil is energized the plunger is retracted. The needle valve that is attached to the plunger is pulled to the full open position and fuel is injected through the valve. When the solenoid is de-energized, spring pressure closes the valve. Since the injection nozzle opening is a fixed size and the fuel pressure is also fixed, the injection amount is determined by the duration time which the needle valve is open (pulse width).