Fuel Injection Diagram: How It Works and the Parts Involved

January 27, 2012

The typical fuel injection diagram consists of 6 main types of parts and is also referred to as the EFI diagram. The sum of all of these fuel injection parts takes the place of the carburetor, and has made it possible for modern vehicles to meet emission requirements.

Parts Found in the Fuel Injection Diagram

  • Fuel Pump
  • Fuel Injectors
  • Fuel Pressure Regulator
  • Engine Control Module/Unit – ECM or ECU
  • Wiring
  • Engine Sensors

The mechanical part of the EFI diagram starts with a high pressure fuel pump, located inside the fuel tank. Fuel is pumped from the tank, through a fuel filter, and to the injectors by way of a supply line. A fuel pressure regulator on the supply line ensures the injectors get constant fuel pressure. When the fuel leaves the injectors, the excess is returned to the tank by way of the return line. This closed loop fuel supply guarantees a consistent spray and amount of fuel from each of the injectors. The injector(s) either sprays the fuel directly into an engine cylinder for burning or into a manifold where it is mixed with air, and drawn into the engine cylinders for burning.

The electrical section of the EFI diagram consists of the ECU, wiring and sensors. A wiring harness connects the injectors to the ECU and to a power source {the battery}. The ECU is also connected to various sensors located within the engine compartment. The ECU monitors engine conditions and the position of the gas pedal in order to determine the correct amount of fuel that needs to be sprayed from each injector.

The operation of a fuel injection system can involve quite a few specialized sensors. For a more complete view of the fuel injection diagram, please consult a fuel injection manual.

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