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Diagnostic Aids

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
Fuel System Diagnosis - High Pressure Side

Step Action Yes No
1 Were you referred to this test from the Engine Cranks but Does Not Run diagnostic? Go to Step 3  Go to Step 2 
2
  1. Remove the fuel return rubber hose from the rear of the left fuel rail 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 it in a clean fuel container.
  3. Start and idle the engine.
  4. Command the fuel rail pressure to 160 MPa with a scan tool.
  5. Observe the fuel hose and container for fuel leakage.
Did fuel flow into the container?		 Go to Step 12  Go to Step 4 
3
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 air duct from the air cleaner assembly and the turbo inlet.
  2. Remove the fuel return rubber hose from the rear of the left fuel rail and plug the hose to prevent fuel leakage.
  3. Remove the relay that supplies ignition 1 voltage to the fuel injection control module (FICM).
  4. Crank the engine for 15 seconds while observing the fuel pressure relief valve hose connection for fuel leakage.
Did fuel leak from the fuel pressure relief valve at the hose connection?		 Go to Step 12  Go to Step 4 
4
IMPORTANT: The engine cranking speed must be more than 150 RPM during the cranking portion of this test.
Always replace the fuel return hose retaining clips on the fuel injectors with new clips after removing.
  1. Remove the relay that supplies the ignition 1 voltage to the FICM, if it was not previously removed.
  2. Remove the fuel return hose from the fuel injectors of the right cylinder bank. Refer to Fuel Injector Return Pipe Replacement - Right .
  3. Connect the yellow hoses from the J 45873  Fuel Return Volume Test Kit to the J 45873-30 Fuel Injector Test Adapters.
  4. Connect the J 45873-30 with yellow hoses to each fuel injector return port of the right cylinder bank, and install the retaining clips.
  5. Install the 4 yellow hoses in the J 45873  graduated cylinders in numerical order.
  6. Connect the fuel return hoses to the J 45873-30 to prevent leakage.
  7. 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 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.
  10. Crank the engine for 15 seconds.
  11. Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the desired quantities.
Were any of the fuel quantities more than the specified values?		 Go to Step 5  Go to Step 6 
5
  1. Remove the fuel feed pipes from any fuel injectors that have high return flow and install the EN 47589  Fuel Pressure Adapter Cap to the fuel rail outlets.
  2. Elevate the 4 hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
  3. Install the 4 yellow hoses in the graduated cylinders in numerical order.
  4. Crank the engine for 15 seconds.
  5. Using the Retesting Fuel Injector Return Flow Values table, measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the desired quantities.
  6. Remove the fuel feed pipes from any uncapped fuel injectors that have high return flow and install the EN 47589  to the fuel rail outlets.
Did you complete the action?		 Go to Step 6  -
6
IMPORTANT: The engine cranking speed must be more than 150 RPM during the cranking portion of this test. Always replace the fuel injector return hose retaining clip.
  1. Remove the fuel return hoses from the fuel injectors of the left cylinder bank. Refer to Fuel Injector Return Pipe Replacement -Left .
  2. Connect the yellow hoses from the to the J 45873-30.
  3. Connect the J 45873-30 with yellow hoses to each fuel injector return port of the left cylinder bank, and install the retaining clips.
  4. Connect the fuel return hoses to the J 45873-30 to prevent leakage.
  5. 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.
  6. Elevate the 4 hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
  7. Install the 4 yellow hoses in the graduated cylinders in numerical order.
  8. Crank the engine for 15 seconds.
  9. Measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the desired quantities.
Were any of the fuel quantities more than the specified values?		 Go to Step 8  Go to Step 7 
7 Were any fuel injector lines capped off during either cylinder bank testing? Go to Step 10  Go to Step 11 
8
  1. Remove the fuel feed pipes from any fuel injectors that have high return flow and install the EN 47589  to the fuel rail outlets.
  2. Elevate the 4 hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
  3. Install the 4 yellow hoses in the graduated cylinders in numerical order.
  4. Crank the engine for 15 seconds.
  5. Using the Retesting Fuel Injector Return Flow Valves table, measure the quantity of fuel in each of the graduated cylinders. Refer to Fuel System Specifications for the desired quantities.
Were the fuel quantities more than the specified value at the uncapped fuel injectors?		 Go to Step 9  Go to Step 10 
9 Repeat the fuel injector return flow test with capping until no fuel injectors have high return fuel flow.
Did you complete the action?		 Go to Step 10  -
10
  1. Replace the fuel injectors that had capped off lines. Refer to Fuel Injector Replacement (Left) or Fuel Injector Replacement (Right) .
  2. Install all disconnected and removed fuel system components.
  3. Start and idle the engine. You may have to prime the fuel system before the engine will start.
  4. Command the fuel pressure control to 160 MPa with a scan tool.
Is the fuel pressure more than 145 MPa?		 Go to Step 13  Go to Step 11 
11 Replace the fuel injection pump. Refer to Fuel Injection Pump Replacement .
Did you complete the replacement?		 Go to Step 13  -
12 Replace the fuel pressure relief valve. Refer to Fuel Pressure Relief Valve Replacement .
Did you complete the replacement?		 Go to Step 13  -
13
IMPORTANT: The fuel system may have to be primed before starting the engine.
  1. Install and connected all fuel system components that were previously removed or disconnected.
  2. Operate the vehicle in order to verify the repairs.
Did you correct the condition?		 System OK Go to Symptoms - Engine Controls 
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