Express 2500 V8-6.6L DSL Turbo VIN 2 (2007)
Fuel Return Line: Testing and Inspection
Fuel Return System Diagnosis
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Testing and Inspection/Initial Inspection and
Diagnostic Overview/Diagnostic Starting Point - Vehicle
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Review Strategy Based Diagnosis for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
Fuel is used to cool and lubricate the fuel injectors and fuel injection pump. The fuel return system is designed to return this fuel to the fuel tank. If the
high side fuel pressure becomes excessive, the fuel rail pressure relief valve releases the fuel into the fuel return system. The return fuel travels through
the diesel fuel conditioning module and the fuel cooler, then to the fuel tank.
Diagnostic Aids
Bent or pinched fuel return lines may cause an external fuel leak or engine performance concerns.
Circuit/System Verification
Inspect the fuel return hoses and lines on the engine and chassis for any external fuel leaks.
Circuit/System Testing
Important: DO NOT apply more than the specified air pressure to the return line.
1. Disconnect the fuel return line at the engine.
2. Remove the fuel filler cap.
3. Apply 1 psi of air into the fuel return at the engine and listen for air flowing from the tank at the filler tube.
4. If air flow was not detected, disconnect the fuel return line at the fuel sender and retest using 1 psi of air.
‹› If air flow was present, replace the fuel sender assembly.
‹› If no air flow was present, inspect for a restricted or a damaged fuel return line. Repair or replace the fuel return line.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Fuel Return Pipe Replacement
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Fuel Sender Assembly Replacement See: Computers and Control Systems/Testing and Inspection/Diagnostic Trouble Code Tests and Associated
Procedures/Verification Tests and Procedures
