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:
| • | The fuel strainer |
| • | The modular fuel sender assembly |
| • | The fuel filter |
| • | The fuel feed pipes and hoses |
| • | The fuel pressure regulator |
| • | The fuel rail |
| • | The fuel injectors |
| • | The fuel return pipes and hoses |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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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.
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A fuel system that drops more than 5 psi in 10 minutes has a leak in one or more areas.
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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.
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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 and may be diagnosed using a scan tool. If an extremely lean condition occurs, the oxygen sensors may drop to less than 500 mV and the fuel injector pulse width will increase.
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When the engine is at idle, the manifold pressure is low. 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.
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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.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you complete the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
Is the fuel pressure within the specified range? | 358-405 kPa (52-59 psi) | |||||||||||
3 | Is the fuel pressure more than the specified value? | 405 kPa (59 psi) | ||||||||||
4 | Visually and physically inspect the fuel system for fuel leaks. Did you find and correct the condition? | |||||||||||
5 | Does the fuel pressure gauge indicate fuel pressure more than the specified value? | 0 kPa (0 psi) | ||||||||||
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Important: When the fuel pump stops running, the fuel pressure may vary slightly, stabilize and remain constant. Observe the fuel pressure on the fuel pressure gauge. Does the fuel pressure decrease more than the specified value in 10 minutes? | 34 kPa (5 psi) | |||||||||||
7 |
Does the fuel pressure gauge indicate constant fuel pressure within the specified range? | 358-405 kPa (52-59 psi) | ||||||||||
Does the fuel pressure gauge indicate a constant fuel pressure? | -- | |||||||||||
Is the fuel pressure suspected of dropping-off during acceleration, cruise, or hard cornering? | -- | |||||||||||
10 | Visually and physically inspect the following components for a restriction:
Did you find and correct the condition? | -- | ||||||||||
11 |
Did you find and correct the condition? | -- | ||||||||||
12 |
Does the fuel pressure decrease within the specified range? | 21-69 kPa (3-10 psi) | Go to Symptoms | |||||||||
Does the fuel pressure decrease within the specified range? | 21-69 kPa (3-10 psi) | |||||||||||
Does the fuel pressure gauge indicate fuel pressure within the specified range? | 358-405 kPa (52-59 psi) | |||||||||||
15 | Visually and physically inspect the fuel rail outlet passages for a restriction. Did you find and correct the condition? | -- | ||||||||||
16 | Visually and physically inspect for the following conditions:
Did you find and correct a condition? | -- | ||||||||||
17 | Replace the modular fuel sender assembly. Refer to Fuel Sender Assembly Replacement . Did you complete the repair? | -- | -- | |||||||||
18 | Locate and repair a loss of vacuum to the fuel pressure regulator. Did you complete the repair? | -- | -- | |||||||||
19 | Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement . Did you complete the repair? | -- | -- | |||||||||
20 | Locate and correct a restriction in the fuel return pipe. Did you complete the repair? | -- | -- | |||||||||
21 |
Does the fuel pressure gauge indicate a constant fuel pressure within the specified range? | 358-405 kPa (52-59 psi) | System OK |
