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Home >> Chevrolet >> 2015 >> Cruze LT, Automatic Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 86 (Engine Controls And Fuel - 1.4L (LUJ LUV) - DTC P0300 To DTC P2635 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> Fuel System Diagnosis (LUJ) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2015 Chevrolet Trax and 2015 Buick Encore. However, it is still accessible from the selected car via links, so may be relevant.

Fuel Pressure Low

  1. Verify none of the conditions listed below exist:
    • Restricted fuel feed pipe
    • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections
    • If a condition exists 

      Repair as necessary.

    • If no conditions exist 
  2. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
    3. CAUTION:

    Do not connect the Fuel Line Shut-off Adapters directly at the fuel rail. The Fuel Line Quick Disconnect Tools will not work at this location. Damage could occur to the fuel rail.

  3. Install the EN 37287  Adapter between the metal chassis fuel return pipe and the nylon engine compartment fuel return pipe.
  4. Open the valve on the EN 37287  Adapter.
  5. Ignition ON, command the Fuel Pump Relay On with a scan tool and bleed the air from the CH 48027  Gauge.
    6. NOTE:

    DO NOT allow the fuel pressure to exceed 517 kPa (75 psi).

  6. Slowly close the valve on the EN 37287  Adapter. while commanding the Fuel Pump Relay On with a scan tool.
  7. Verify that the fuel pressure increases to greater than 345 kPa (50 psi).
    • If less than 345 kPa (50 psi) 

      Replace the G12 Fuel Pump.

    • If greater than 345 kPa (50 psi) 

      Replace the Q18 Fuel Pressure Regulator.

Fuel Pressure High

  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
  2. Disconnect the fuel return pipe at the fuel rail.
  3. Attach a length of flexible fuel hose to the fuel rail return pipe.
  4. Place the open end of the flexible fuel hose into an approved gasoline container.
  5. Ignition ON, command the Fuel Pump Relay On with a scan tool.
  6. Verify the fuel pressure is between 276-345 kPa (40-50 psi) with the fuel pump running.
    • If less than 345 kPa (50 psi) 

      Locate and replace the restricted fuel return pipe.

    • If greater than 345 kPa (50 psi) 
  7. Verify none of the conditions listed below exist:
    • Restricted fuel rail return pipe
    • Restricted fuel rail outlet passage
    • If a condition exists 

      Repair as necessary.

    • If no conditions exist 

      Replace the Q18 Fuel Pressure Regulator.

Fuel Pressure Leaks Down

  1. Disconnect the fuel pressure regulator vacuum hose.
  2. Engine idling, apply 12-14 inches of vacuum to the fuel pressure regulator with a hand held vacuum pump and verify the fuel pressure decreases 21-69 kPa (3-10 psi).
    • If the fuel pressure does not decrease 

      Replace the fuel pressure regulator.

    • If the fuel pressure decreases 
  3. Ignition OFF, verify none of the conditions below exist:
    • Damaged, leaking, or restricted fuel pressure regulator hose
    • Restricted vacuum source
    • If a condition exists 

      Repair as necessary.

    • If no conditions exist 
  4. Ignition ON, command the Fuel Pump Relay On with a scan tool and inspect for a fuel leak from the fuel pressure regulator vacuum port.
    • If there is a fuel leak 

      Replace the fuel pressure regulator.

    • If there is no fuel leak 
  5. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
    6. CAUTION:

    Do not connect the Fuel Line Shut-off Adapters directly at the fuel rail. The Fuel Line Quick Disconnect Tools will not work at this location. Damage could occur to the fuel rail.

  6. Install the EN 37287  Adapters between the metal chassis fuel pipes and the nylon engine compartment fuel pipes.
  7. Open the valves on the EN 37287  Adapters.
  8. Ignition ON, command the Fuel Pump Relay On with a scan tool and bleed the air from the CH 48027  Gauge.
  9. Command the Fuel Pump Relay On and then Off with a scan tool.
  10. Close the valve on the fuel feed pipe EN 37287  Adapter.
  11. Monitor the CH 48027  Gauge for 1 minute and verify that the fuel pressure does not decrease.
    • If the fuel pressure does not decrease 

      Replace the G12 Fuel Pump.

    • If the fuel pressure decreases 
  12. Ignition OFF, open the valve on the fuel feed pipe EN 37287  Adapter.
  13. Ignition ON, command the Fuel Pump Relay On and then Off with a scan tool.
  14. Close the valve on the fuel return pipe EN 37287  Adapter.
  15. Monitor the CH 48027  Gauge for 1 minute and verify that the fuel pressure does not decrease.
    • If the fuel pressure does not decrease 

      Replace the Q18 Fuel Pressure Regulator.

    • If the fuel pressure decreases 

      Locate and replace the leaking Q17 Fuel Injector.

Fuel Pressure Drops Off

  1. Disconnect the fuel pressure regulator vacuum hose.
  2. Engine idling, apply 12-14 inches of vacuum to the fuel pressure regulator with a hand held vacuum pump and verify the fuel pressure decreases 21-69 kPa (3-10 psi).
    • If the fuel pressure does not decrease 

      Replace the fuel pressure regulator.

    • If the fuel pressure decreases 
  3. Ignition OFF, verify none of the conditions below exist:
    • Damaged, leaking, or restricted fuel pressure regulator hose
    • Restricted vacuum source
    • If a condition exists 

      Repair as necessary.

    • If no conditions exist 
  4. Ignition ON, command the Fuel Pump Relay On with a scan tool and inspect for a fuel leak from the fuel pressure regulator vacuum port.
    • If there is a fuel leak 

      Replace the fuel pressure regulator.

    • If there is no fuel leak 
  5. Verify none of the conditions listed below exist:
    • Restricted fuel feed pipe
    • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections
    • If a condition exists 

      Repair as necessary.

    • If no conditions exist 

      Replace the G12 Fuel Pump.

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