System Description
The powertrain control module (PCM) enables the fuel pump relay when the ignition switch is turned ON. The PCM will disable the fuel pump relay within 2 seconds unless the PCM detects ignition reference pulses. The PCM continues to enable the fuel pump relay as long as ignition reference pulses are detected. The PCM disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON.
The Fuel System is a returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.
The fuel tank stores the fuel supply. An electric turbine style fuel pump attaches to the fuel sender assembly inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel sender assembly. The function of the venturi pump is to fill the fuel sender assembly reservoir. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel injection system. The fuel pump and sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.
Test Description
The numbers below refer to the numbers on the diagnostic table.
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This step verifies that the fuel pump is operating.
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This step tests for an internal fuel leak. If the fuel pressure drops during this test, then an internal loss of pressure is indicated.
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This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.
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This step verifies that a circuit condition is not the cause of a fuel pressure concern. Inspect all fuel pump electrical circuits thoroughly.
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This step tests for a leaking fuel injector, or fuel pressure regulator. If the fuel pressure remains constant during this test, the fuel injectors are not leaking fuel.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Fuel System Description | ||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
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Important: Inspect the fuel system for damage, or external leaks, before proceeding with this diagnostic.
Does the fuel pump operate? | -- | Go to Step 3 | ||||||
3 |
Important: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.
Caution: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gage. Place the towel in an approved container when the connection of the fuel pressure gage is complete. Important:
Is the fuel pressure within the specified value? | 384-425 kPa (56-62 psi) | Go to Step 4 | Go to Step 8 | ||||
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Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant. Observe the fuel pressure gage for 1 minute. Does the fuel pressure drop more than the specified value? | 34 kPa (5 psi) | Go to Step 7 | Go to Step 5 | |||||
5 |
Does the fuel drop more than the second specified value? | 69 kPa (10 psi) 14 kPa (2 psi) | Go to Step 12 | Go to Step 6 | ||||
6 |
Do any of the scan tool parameters indicate a lean condition? | -- | Go to Step 9 | |||||
Does the fuel pressure remain constant? | -- | Go to Step 12 | Go to Step 11 | |||||
8 | Is the fuel pressure more than the specified value? | 427 kPa (62 psi) | Go to Step 12 | Go to Step 9 | ||||
9 | Inspect the fuel feed pipe for a restriction. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||
Inspect the harness connectors and ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | |||||
Did you complete the replacement? | -- | Go to Step 13 | -- | |||||
12 | Replace the fuel pump. Refer to Fuel Sender Assembly Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||
13 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 3 | ||||
