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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (Engine Controls And Fuel - 2.8L (LWN) Diesel - Diagnostic Information And Procedures (3 Of 3)) >> Diagnostic Information and Procedures >> Fuel System Diagnosis - High Pressure Side >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

Test 1

  1. Ignition/Vehicle & All vehicle systems - Off
    2. NOTE:
    • In order to perform step 2 - 5, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur.
    • Leave the electrical connector connected.
  2. Disconnect the component : Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
  3. Install suitable hose to the component : Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.
  4. Engine - Cranking - Until air is purged from the hose
  5. Engine - Cranking - For 15 s

    Verify the container contains less than 15 mL (0.5 US fl oz)

    • If 15 mL (0.5 US fl oz) or greater 

      Replace the component : Q18B Fuel Pressure Regulator 2

    • Go to next step : If less than 15 mL (0.5 US fl oz) 
  6. Ignition/Vehicle & All vehicle systems - Off
  7. Install the component : Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
  8. Disconnect the electrical connector : Q17 Fuel Injector - All
  9. Disconnect the component : Fuel Injection Fuel Return Pipe - Plug the fuel return hose(s) in order to prevent leakage. Refer to : Fuel Injection Fuel Return Pipe Replacement
  10. Engine - Cranking - For 15 s
  11. Verify the condition does not exist : Leaking @ Fuel Injection Fuel Return Pipe
    • If a condition exists 

      Replace the appropriate component : Q17 Fuel Injector

    • Go to next step : If no condition exists 
  12. Ignition/Vehicle & All vehicle systems - Off
  13. Install the component : Fuel Injection Fuel Return Pipe
  14. Perform the following steps :
    1. Disconnect the electrical connector : Q17 Fuel Injector - All
    2. Disconnect the electrical connector : E12 Glow Plug - All - Secure and insulate the connection using electrical tape.
    3. Remove the component : E12 Glow Plug - All
    4. Place and hold a clean shop towel over the component : Threaded Hole @ Cylinder Head - Glow Plug
    5. Engine - Cranking - For 6 s

      Verify the condition does not exist : Fuel On Shop Towel

    • If a condition exists 

      Replace the appropriate component : Q17 Fuel Injector

    • Go to next step : If no condition exists 
  15. Test or replace the component : G18 High Pressure Fuel Pump

Test 2

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Perform the following procedure/test : Fuel Injector Balance Test 

    Verify the procedure/test passes.

    • If the procedure/test does not pass 

      Replace the component that failed the test : Q17 Fuel Injector

    • Go to next step : If the procedure/test passes 
  3. Engine - Idling
    4. NOTE:

    Fuel Rail Pressure - Maximum @ At Idle Speed = 100 MPa (14, 504 PSI)

  4. Perform the scan tool control function : Fuel Rail Pressure - Increase & Decrease

    Verify the following parameters are within 690 kPa (100 PSI) of each other :

    • Desired Fuel Rail Pressure
    • Fuel Rail Pressure Sensor 1
    • If not within 690 kPa (100 PSI) of each other 

      Replace the component : Q18A Fuel Pressure Regulator 1

    • Go to next step : If within 690 kPa (100 PSI) of each other 
  5. Ignition/Vehicle & All vehicle systems - Off
    6. NOTE:
    • In order to perform step 6 - 9, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur.
    • Leave the electrical connector connected.
  6. Disconnect the component : Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
  7. Install suitable hose to the component : Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.
  8. Engine - Idling - Until air is purged from the hose
  9. Engine - Idling - For 15 s

    Verify the container contains less than 15 mL (0.5 US fl oz)

    • If 15 mL (0.5 US fl oz) or greater 

      Replace the component : Q18B Fuel Pressure Regulator 2

    • Go to next step : If less than 15 mL (0.5 US fl oz) 
  10. Ignition/Vehicle & All vehicle systems - Off
  11. Install the component : Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
  12. Disconnect the electrical connector : Q17 Fuel Injector - All
  13. Disconnect the component : Fuel Injection Fuel Return Pipe - Plug the fuel return hose(s) in order to prevent leakage. Refer to : Fuel Injection Fuel Return Pipe Replacement
  14. Engine - Cranking - For 15 s
  15. Verify the condition does not exist : Leaking @ Fuel Injection Fuel Return Pipe
    • If a condition exists 

      Replace the appropriate component : Q17 Fuel Injector

    • Go to next step : If no condition exists 
  16. Ignition/Vehicle & All vehicle systems - Off
  17. Install the component : Fuel Injection Fuel Return Pipe
  18. Perform the following steps :
    1. Disconnect the electrical connector : Q17 Fuel Injector - All
    2. Disconnect the electrical connector : E12 Glow Plug - All - Secure and insulate the connection using electrical tape.
    3. Remove the component : E12 Glow Plug - All
    4. Place and hold a clean shop towel over the component : Threaded Hole @ Cylinder Head - Glow Plug
    5. Engine - Cranking - For 6 s

      Verify the condition does not exist : Fuel On Shop Towel

    • If a condition exists 

      Replace the appropriate component : Q17 Fuel Injector

    • Go to next step : If no condition exists 
  19. Test or replace the component : G18 High Pressure Fuel Pump
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