Circuit 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 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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To relieve the fuel pressure, refer to Fuel Pressure Relief Procedure . 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.
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A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more of the following areas:
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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.
| • | The fuel pump check valve |
| • | The fuel pump flex pipe |
| • | The fuel injectors |
| • | The fuel filter/regulator |
Important: Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.
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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.
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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.
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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.
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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.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
Important: To avoid false fuel pressure readings, thoroughly bleed all air out of the fuel pressure gauge. Important: The fuel pump will run for approximately 2 seconds. Cycle the ignition switch as necessary in order to achieve the highest possible fuel pressure. Is the fuel pressure near the specified value? | 380-410 kPa (55-60 psi) | |||||||||||
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Important: The fuel pressure will vary slightly when the fuel pump stops running, the fuel pressure should stabilize and remain constant. Note the fuel pressure after the fuel pump stops running. Does the fuel pressure drop more than the specified value in 5 minutes? | 50 kPa (5 psi) | |||||||||||
4 |
Does the fuel pressure drop more than the second specified value in 5 minutes? | 69 kPa (10 psi) 14 kPa (2 psi) | ||||||||||
Is the fuel pressure suspected of dropping-off during acceleration, cruise or hard cornering? | -- | |||||||||||
6 | Inspect the following items for a restriction:
Was a restriction found? | -- | ||||||||||
7 |
Was a problem found in any of these areas? | -- | ||||||||||
8 |
Is the fuel pressure near the specified value? | 400 kPa (58 psi) | System OK | |||||||||
9 |
Important: Repeat pressurizing the fuel system with the scan tool as necessary to achieve the highest possible fuel pressure. Does the fuel pressure remain constant? | -- | ||||||||||
10 |
Does the fuel pressure indicated by the fuel pressure gauge remain constant? | -- | ||||||||||
Is the fuel pressure above the specified limit? | 410 kPa (60 psi) | |||||||||||
Did you find a condition? | ||||||||||||
Does the fuel pressure indicated on the fuel pressure gauge rise above the first specified value? | 414 kPa (60 psi) 450 kPa (65 psi) | |||||||||||
14 | Refer to Fuel Pump Electrical Circuit Diagnosis to diagnose the fuel pump electrical circuit. Was a condition found with the fuel pump electrical circuit? | -- | ||||||||||
15 | Inspect the following items:
Was a condition found in any of these areas? | -- | ||||||||||
16 | Replace the fuel filter/regulator assembly. Is the action complete? | -- | System OK | -- | ||||||||
17 | Replace the modular fuel sender. Refer to Fuel Sender Assembly Replacement . Is the action complete? | -- | System OK | -- | ||||||||
Locate and replace any leaking fuel injectors. Refer to Fuel Injector Replacement . Is the action complete? | -- | System OK | -- | |||||||||
19 | Repair the condition as necessary. Is the action complete? | -- | System OK | -- |
