Do-It-Yourself Knowing Fuel System Function and Components

This diagram may help you to understand how fuel system components works and how they relate to one another before doing any fuel pressure testing.

1. Fuel Tank: container that holds vehicle’s supply of fuel.
2. Fuel Pump Filter: usually located in fuel tank, prevent foreign particles from reaching the fuel pump.
3. Fuel Pump: mounted in the fuel tank or on the frame which pumps fuel into the fuel system at a constant pressure.
4. Return Line: path way for excess fuel to return to the fuel tank.
5. Pressure Line: a pressurized fuel line that carries fuel from the fuel tank to the fuel injectors.
6. Fuel Filter: located in-line with the pressure line to prevent foreign particles from reaching the fuel injectors. The only fuel system component that requires periodic replacement.
7. Fuel Rail Test Port: a schrader valve located on the fuel rail that allows easy connection of a fuel pressure gauge to measure fuel pressure.
8. Fuel Pressure Regulator (vacuum actuated (compensated) fuel pressure regulators): connected across the pressure line and return line, used to keep a constant fuel pressure drop across the fuel injectors.
9. Fuel Rail: bolted to the intake manifold, to hold the fuel injectors in place and to deliver pressurized fuel to the fuel injectors.
10. Fuel Injectors: a precision valve that is controlled by a solenoid, it contain a filter used to prevent very small particles from clogging the valve.