Electrical Signal:
1. ECU Control: The ECU receives signals from various sensors in the engine, such as the camshaft position sensor and crankshaft position sensor, to determine the exact timing when each injector needs to fire.
2. Driver Circuit: The ECU then sends electrical signals to the injector driver circuit. This circuit amplifies the low-current signal from the ECU to the higher current required to activate the injectors.
3. Injector Activation: The amplified electrical signal from the injector driver circuit reaches the injector solenoid. This solenoid is essentially an electromagnetic valve that opens and closes to allow fuel into the engine's cylinders. When energized by the electrical signal, the solenoid moves a plunger or armature within the injector, allowing fuel to be released.
Mechanical Action:
1. Camshaft Rotation: The camshaft in the engine's valvetrain rotates in sync with the crankshaft. On the camshaft, there are lobes or eccentric surfaces specifically designed to actuate the injector's mechanical components.
2. Pushrods and Rocker Arms: The camshaft lobes directly or indirectly (via pushrods and rocker arms in traditional setups) push on small mechanical levers called poppets or tappets.
3. Injector Needle Valve: The poppet or tappet exerts mechanical force on the injector's needle valve assembly, which is part of the fuel injector mechanism. This mechanical action lifts the needle valve off its seat, allowing fuel under pressure from the fuel rail to be sprayed into the engine's cylinders.
So, in summary, the injectors in a Ford 302 engine in an F150 are fired by the combined action of electrical signals from the ECU and the mechanical motion of the camshaft, which allows for precise timing of fuel injection.
