Fuel System Pressure Test

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

SYSTEM DESCRIPTION
Proper fuel pressure is necessary to maintain efficient engine operation and emission levels, if fuel pressure is not within specifications vehicle driveability may be affected or emission levels elevated.

The fuel system contains the following components:
^ Fuel strainer
^ Modular fuel sender assembly
^ Fuel filter
^ Fuel feed pipes/hoses
^ Fuel pressure regulator
^ Fuel rail
^ Fuel injectors
^ Fuel return pipes/hoses

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the fuel systems ability to achieve a specific fuel pressure range. It may be necessary to cycle the fuel pump several times to achieve the pressure range.
6. This step tests fuel pressure. A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more areas.
8. This step tests the fuel systems ability to maintain a specific fuel pressure. It may be necessary to cycle the fuel pump several times to achieve the pressure range.
9. This step tests fuel pressure. Fuel pressure that drops-off during acceleration, cruise, or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging or misfire and may be diagnosed using a scan tool. If an extremely lean condition occurs, the oxygen sensors may drop below 500 mV and the fuel injector pulse width will increase.
13. This step tests fuel pressure. When the engine is at idle, the manifold pressure is low, high vacuum. This low pressure, high vacuum, is applied to the fuel pressure regulator diaphragm, the result is lower fuel pressure. The fuel pressure at idle will vary slightly as the pressure changes, but the fuel pressure at idle should always be less than the fuel pressure noted in Step 2 with the engine OFF.
14. This test determines if the high fuel pressure is due to a restricted fuel return pipe or fuel pressure regulator. A rich condition may cause a DTC P0132 or DTC P0172 to set. Driveability conditions associated with rich conditions can include hard starting, followed by black smoke, and a strong sulfur smell in the exhaust.