Fuel Injection

Step by step illustrated explanation of an automotive fuel injection system.

Step 1
- Fuel injection is used to supply an internal combustion engine with the proper amount of fuel at any given engine speed. Once fuel enters the fuel tank its picked up by the fuel pump which is situated inside the gas tank. This fuel pump is controlled by a relay located in the PDC power distribution center which is activated by the computer.

Fuel Pump In-Tank

Step 2 - Once pressurized, the fuel travels along the bottom of the vehicle through fuel lines toward the fuel filter.

Fuel Lines

Step 3 - Fuel then travels to the fuel filter where its cleaned before continuing to the injection rail.

Fuel Filter

Step 4 - After being cleansed by the fuel filter, pressurized fuel enters the fuel rail where its distributed to individual injectors.

Fuel Rail

Step 5 - A fuel pressure regulator is used to maintain and adjust pressure while the engine is in use, this device is only used in fuel return style injection systems. Some fuel injected vehicles are fitted with a regulator at the fuel pump.


Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-01-08)