Savana 4500 V8-6.6L DSL Turbo (2009)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis
Fuel System Diagnosis
Diagnostic Instructions
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Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
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Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
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Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure Instructions)
provides an overview of each diagnostic category.
Circuit/System Description
Fuel is drawn by the fuel injection pump through a pre-filter screen in the tank. Fuel flows to the diesel fuel conditioning module (DFCM) , which
combines a water separator, an electric fuel prime pump, fuel heater element, and a filter element. The fuel is then delivered to a second screw on fuel
filter and the high-pressure pump. An integrated electric fuel prime pump is used to prime the fuel system after changing the fuel filter or servicing the
fuel system. The mechanical fuel injection pump at the front of the engine valley includes the fuel supply pump and the high-pressure pump.
High Pressure System
The much larger section of the fuel injection pump assembly is the high-pressure fuel injection pump. The pump is engine-driven by the camshaft gear.
From the high-pressure pump, the pressurized fuel flows to the left fuel rail. A balance pipe from the center of the left fuel rail then feeds the right fuel
rail. Each fuel rail supplies one bank of 4 fuel injectors. The fuel rail pressure (FRP) sensor is mounted in the right fuel rail.
Return System
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
A Cranks But Will Not Run or Hard Start symptom may exist if air is being drawn into the fuel injection system due to the following conditions:
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Deformed or cut O-rings at the fuel supply line connections
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Improperly seated fuel supply line fittings
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Porous or weathered rubber fuel supply lines
Reference Information
Special Tools
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CH-48027 Digital Pressure Gage
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J 44581 Fuel Line Disconnect Tool
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EN-47969 Fuel Supply Diagnostic Hose
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J 35555 Metal MityVac
Circuit/System Verification
Observe the Actual Fuel Rail Pressure parameter with a scan tool. During engine cranking, the pressure should be at least 10 MPa. With the engine
running at idle the pressure should be close to the Desired Fuel Rail Pressure. As the engine RPMs increase, the Desired Fuel Rail Pressure and the
Actual Fuel Rail Pressure should closely match each other.
