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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 94 (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 car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

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. Perform the scan tool control function: Engine Speed - Increase - 1, 500 RPM - 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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