CHECKING THE HIGH-SIDE FUEL SYSTEM

For a complete wiring diagram Refer to Section 8W

Possible Causes

AIR IN FUEL SYSTEM

SCAN TOOL TESTS

FUEL PRESSURE SOLENOID

FUEL PRESSURE SOLENOID RETURN VOLUME TEST

FUEL PUMP

FUEL SYSTEM LEAK

INJECTOR RETURN VOLUME TEST

Diagnostic Test

1.CHECKING FUEL PRESSURE

NOTE: The Low/Supply Side Fuel System must be working properly for this test to be valid. Refer to the Service Information and Perform the Low/Supply Side Fuel System Test before continuing.

NOTE: This vehicle is not equipped with an in-tank fuel lift pump. The high pressure fuel pump draws (vacuums) the fuel from the fuel tank. Even a very small leak in the fuel supply system between the fuel tank and high-pressure pump can cause driveability problems and dtc's to set.

NOTE: This test requires two people. One person to test drive the vehicle while a technician observes the scan tool readings

NOTE: The Fuel Pressure reading should follow (trail) closely to the Fuel Pressure Desired/Setpoint reading.

Does the Fuel Pressure reading follow closely to the Fuel Pressure Desired/Setpoint reading?

Yes

Test Complete.

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2.FUEL SYSTEM LEAK

WARNING: HIGH-PRESSURE FUEL LINES DELIVER DIESEL FUEL UNDER EXTREME PRESSURE FROM THE INJECTION PUMP TO THE FUEL INJECTORS. THIS MAY BE AS HIGH AS 23,200 PSI (1600 BAR). USE EXTREME CAUTION WHEN INSPECTING FOR HIGH-PRESSURE FUEL LEAKS.

WARNING: FUEL UNDER THIS AMOUNT OF PRESSURE CAN PENETRATE SKIN CAUSING PERSONAL INJURY OR DEATH. INSPECT FOR HIGH-PRESSURE FUEL LEAKS WITH A SHEET OF CARDBOARD. WEAR SAFETY GOGGLES AND ADEQUATE PROTECTIVE CLOTHING WHEN SERVICING FUEL SYSTEM.

Is there any evidence of leakage?

Yes

Repair as necessary in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

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3.CHECKING FOR AIR IN FUEL SYSTEM

NOTE: If there is air in the fuel system, the Actual Fuel Pressure will oscillate more than 100 spi above and/or below the Fuel Pressure Setpoint.

Does Actual Fuel Pressure oscillate more than 100 psi above and/or below the Fuel Pressure Setpoint?

Yes

Refer to the Service Information to purge air from the fuel system.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

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4.FUEL PRESSURE SOLENOID

NOTE: A sticking Fuel Pressure Solenoid is indicated by Actual Fuel Pressure gradually dropping below the Fuel Pressure Setpoint then suddenly increasing (spiking) above the Fuel Pressure Setpoint.

Does Actual Fuel Pressure gradually decrease then suddenly increase (spike) above the Fuel Pressure

Yes

Replace the Fuel Pressure Solenoid in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

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5.SCAN TOOL TESTS

Were any problems found?

Yes

Diagnose and/or repair as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

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6.INJECTOR RETURN VOLUME TEST

Did the Injectors pass the Return Volume Test?

Yes

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Refer to the Service Information and replace injector(s) as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

7.FUEL PRESSURE SOLENOID RETURN VOLUME TEST

Did the Fuel Pressure Solenoid pass the Return Volume Test?

Yes

Replace the Fuel Pump in accordance with the Service Information.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Refer to the Service Information and replace the Fuel Pressure Solenoid.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).