GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 6.6L (LBZ and LLY) 🢒 Fuel Leak Diagnosis

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Testing
  1. Remove the air cleaner assembly. Refer to Air Cleaner Assembly Replacement .
  2. Clean all of the fuel lines between the fuel injection pump and the fuel injectors using brake cleaning solvent, and let dry.
  3. Add 8 ounces of oil dye to the fuel tank. On dual tanks, add the dye to the front, or primary tank. Refer to Fuel System Description .
  4. Start and idle the engine for 3-5 minutes.
  5. Command the fuel pressure control to 160 MPa (23,206 psi) with a scan tool.
  6. Inspect for fuel leaks around the fuel injection pump, fuel rails, and fuel injector supply lines with a J 28428-E High Intensity Black Light Kit.

    7. Tighten or replace any leaking lines or components. Refer to the following:

    •  Fastener Tightening Specifications
    •  Fuel Injection Line Routing Diagram
    •  Fuel Injection Fuel Return Pipe Replacement - Left Side
    •  Fuel Injection Fuel Return Pipe Replacement - Right Side
    •  Fuel Injection Fuel Rail Assembly Replacement - Bank 1
    •  Fuel Injection Fuel Rail Assembly Replacement - Bank 2
    •  Fuel Return Junction Block Replacement
    •  Fuel Injection Pump Replacement
    •  Fuel Injector Replacement
  7. A fuel leak may be caused by restricted return fuel lines. Refer to Fuel Return System Diagnosis .