Electronic Fuel Injection (EFI)

In an EFI system, solenoids are primarily used in fuel injectors to control fuel delivery into the engine.

1. An electrical signal from the Engine Control Unit (ECU) activates the solenoid in a fuel injector.

2. When activated, the solenoid moves a plunger or needle valve, which opens the injector nozzle, allowing fuel to spray into the combustion chamber.

3. The ECU controls the timing and duration of the solenoid’s activation to precisely manage the amount of fuel injected, aligning it with the engine's needs for optimal combustion.

4. This control enables precise metering of fuel, contributing to the efficiency and emissions performance of the engine.

Components of an EFI System

1. Fuel Tank: Stores the fuel to be supplied to the engine.

2. Fuel Pump: Draws fuel from the tank and delivers it under pressure to the injectors. Typically an electric pump located in or near the fuel tank.

3. Fuel Injectors: Small electrically controlled valves that spray fuel into the intake manifold or directly into the combustion chamber.

4. Fuel Pressure Regulator: Maintains a constant fuel pressure for the injectors to ensure consistent fuel delivery.

5. Engine Control Unit (ECU): The brain of the EFI system. It monitors various engine parameters and controls the fuel injectors’ timing and duration.

6. Sensors:

   • Mass Air Flow (MAF) Sensor: Measures the air entering the engine, allowing the ECU to calculate the appropriate fuel amount.

   • Oxygen (O2) Sensor: Detects the oxygen level in exhaust gases, providing feedback to the ECU for adjusting the air-fuel mixture.

   • Throttle Position Sensor (TPS): Measures the throttle valve position to determine the engine load.

   • Engine Coolant Temperature (ECT) Sensor: Monitors the engine’s temperature to adjust the fuel-air mix for optimal performance.

   • Manifold Absolute Pressure (MAP) Sensor: Measures pressure in the intake manifold to estimate engine load.

   • Crankshaft and Camshaft Position Sensors: Provide the ECU with the engine's timing and positioning information.

7. Fuel Rail: A tube that supplies fuel to the injectors, keeping the fuel ready for injection.