Sierra 3500 4WD V8-6.6L DSL Turbo VIN 2 (2004)
Fuel Return Line: Description and Operation
FUEL FEED AND RETURN PIPES
The fuel feed pipe carries fuel from the fuel tank to the fuel injector control module. The fuel return pipe carries fuel from the fuel rail assemblies back
to the fuel tank. The fuel pipes consist of 2 sections:
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The rear fuel pipe assemblies are located from the top of the fuel tank to the chassis fuel pipes. The rear fuel pipes are constructed of steel with
sections of rubber hose covered with braiding.
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The chassis fuel pipes are located under the vehicle and connect the rear fuel pipes to the fuel rail pipes. These pipes are constructed of steel with
sections of rubber hose covered with braiding.
FUEL INJECTORS AND RETURN LINES
A fuel injector is a solenoid device, controlled by the fuel injection control module (FICM), that meters pressurized fuel to a single engine cylinder.
The engine control module (ECM) energizes the low-impedance injector solenoid to open a normally closed valve. Fuel pressure is released from
above the fuel injector pintle, and is returned to the fuel tank through the fuel return lines. The difference in fuel pressure above and below the pintle
causes the pintle to open. Fuel from the fuel injector tip is sprayed directly into the combustion chamber on the compression stroke of the engine.
