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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls - 6.6L - Troubleshooting & Diagnosis) >> Fuel System Diagnosis - High Pressure Side >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
IMPORTANT: If you were not referred to this test from another diagnostic, do not perform this procedure. Only perform this test when the fuel is more than 18°C (65°F).
  1. Remove the fuel pressure relief valve return hose and plug the hose to prevent fuel leakage.
  2. Install a section of rubber fuel hose on the fuel pressure relief valve connection and place loose end of hose into a clean fuel container.
    • If the engine cranks but does not start, crank engine for 15 seconds. Observe for fuel leaking from fuel pressure relief valve.
    • If the engine starts and runs, idle the engine while commanding the fuel rail pressure to 180 MPa with a scan tool. Observe for fuel leaking from fuel pressure relief valve.
    3. IMPORTANT: Always replace the fuel return hose retaining clips on the fuel injectors with new clips after removing.
  3. Remove the fuel return hose from the fuel injectors of the right cylinder bank. Refer to Fuel Injector Return Pipe Replacement - Right .
  4. Connect the yellow hoses from the J 45873  to the Fuel Injector Test Adapters. See Special Tools .
  5. Connect the Fuel Injector Test Adapters with yellow hoses to each fuel injector return port of the right cylinder bank, and install the retaining clips.
  6. Install the 4 yellow hoses in the J 45873  graduated cylinders in numerical order. See Special Tools .
  7. Connect the fuel return hoses to the J 45873-31 to prevent leakage.
    • If the engine starts and runs, idle the engine until fuel start dripping into all the graduated cylinders and yellow hoses are full of fuel.
      • IMPORTANT: The engine cranking speed must be more than 150 RPM during the cranking portion of this test.
    • If the engine does not start, crank the engine in 15-second intervals, with 1 minute cooling time between intervals, until fuel starts to flow into all of the graduated cylinders.
  8. Elevate the 4 yellow hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
  9. Install the 4 yellow hoses in the J 45873  graduated cylinders in numerical order. See Special Tools .
    • If the engine starts and runs, idle the engine for 15 seconds.
    • If the engine does not start, crank the engine for 15 seconds.
  10. Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the desired quantities.
    • If high return flow was recorded, remove the fuel feed pipes from any fuel injectors that have high return flow and install the EN 47589  to the fuel rail outlets. See Special Tools .
  11. Retest the fuel return flow, using the Fuel System Specifications , and cap any additional high return flow injectors.
  12. Remove the fuel return pipes from the fuel injectors of the left cylinder bank and repeat the fuel return flow test previously preformed on the right cylinder bank.
    13. IMPORTANT: During replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis .
  13. Start and idle the engine. You may have to prime the fuel system before the engine will start.
  14. Command the fuel pressure control to 180 MPa with a scan tool.
  15. Install and connect all fuel system components that were previously removed or disconnected.
    IMPORTANT: The fuel system may have to be primed before starting the engine.
  16. Operate the vehicle in order to verify the repairs.
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