Fuel System Diagnosis

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

Schematic:

SYSTEM DESCRIPTION
When the ignition switch is turned ON, the Powertrain Control Module (PCM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will turn the in-tank fuel pump OFF 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running. The in-tank fuel pump is an electric pump within an integral reservoir. The in-tank fuel pump supplies fuel through the fuel feed pipe and the in-line fuel filter to the fuel rail assembly. The fuel pump is designed to provide fuel at a pressure above the pressure needed by the fuel injectors. A fuel pressure regulator, attached to the fuel rail, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned to the fuel tank by a separate fuel return pipe.

TEST DESCRIPTION
Numbers below refer to the step numbers on the Diagnostic Table.
2. 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. A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more areas.
8. 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. 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. 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.