Fuel System Diagnosis
CIRCUIT DESCRIPTIONWhen 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 OFF the in-tank fuel pump after 2 seconds since the ignition is turned ON or after 2 seconds once 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 an in-line fuel filter/regulator assembly to the fuel rail assembly. The fuel pump is designed to provide fuel at a pressure above the pressure that is needed by the fuel injectors.
Diagnostic Chart (Part 1 Of 3):
Diagnostic Chart (Part 2 Of 3):
Diagnostic Chart (Part 3 Of 3):
TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. To relieve the fuel pressure, refer to Fuel Pressure Release. When the ignition switch is ON and the fuel pump is running, the fuel pressure indicated by the fuel pressure gauge should be 380-410 kPa (55-60 psi). This pressure is controlled by the amount of pressure the spring inside the fuel pressure regulator can provide.
3. A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more of the following areas:
^ The fuel pump check valve
^ The fuel pump flex pipe
^ The fuel injectors
^ The fuel filter/regulator
5. 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. A lean condition can be diagnosed using a scan tool. If an extremely lean condition occurs, the oxygen sensors will stop toggling. The oxygen sensor output voltages will drop below 500 mV. Also, the fuel injector pulse width will increase.
IMPORTANT: Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.
11. A rich condition may result from the fuel pressure being above 410 kPa (60 psi). A rich condition may cause a DTC P0132 or a 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.
12. This test determines if the high fuel pressure is due to a restricted fuel return pipe or if the high fuel pressure is due to a faulty fuel pressure regulator.
13. Restricting the fuel flow causes the fuel pressure to rise above the regulated fuel pressure. Using a scan tool to pressurize the system, the fuel pressure should rise above 410 kPa (60 psi) as the valve is closed.
18. Check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking.