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GM/Detroit 6.5L – Fuel System – FUEL RETURN SYSTEM

The fuel return system uses the following hoses and pipes (figure 4-8):
• The housing pressure regulator is connected to the return system by a hose and two clamps
(view A).
• Injection nozzles are individually connected to a return pipe by short lengths of hose (view B)
• The rear fittings of nozzles for cylinder 7 and 8 have caps and clamps (view C).
• The return hoses for cylinders 1 and 2 connect to a center pipe (view D).
• The injection pump return hose connects to the same center pipe as cylinders 1 and 2. The injection return hose also connects to a pipe mounted under the right underside of the intake manifold (view E).
• At the rear of the engine, the return system pipe under the intake manifold connects to a series of
hoses and pipes that send fuel back to the fuel tank (view F).

During diagnosis of the injection pump, the return system is checked for restrictions. Any blockage in the path of fuel leaving the injection pump will greatly affect the performance of the engine.


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