Savana 3500 V8-6.6L DSL Turbo VIN 2 (2006)
Fuel Pressure: Testing and Inspection
Fuel System Diagnosis - High Pressure Side
FUEL SYSTEM DIAGNOSIS - HIGH PRESSURE SIDE
DIAGNOSTIC FAULT INFORMATION
Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Powertrain Management/Computers and
Control Systems/Testing and Inspection/Diagnostic Trouble Code Tests and Associated Procedures
CIRCUIT/SYSTEM DESCRIPTION
High Pressure System
The fuel injection pump at the front of the engine valley includes a fuel supply pump and a high-pressure pump. Fuel is drawn by the fuel supply pump
from the primary fuel tank and delivered to the high-pressure pump. The pump is engine-driven by the camshaft gear. High pressure fuel is regulated
by the fuel pressure regulator mounted on the fuel injection pump. From the high-pressure pump, the fuel moves to the left and right fuel rails through
high pressure medal lines. Each fuel rail distributes high pressure fuel to one bank of 4 fuel injectors. The fuel pressure relief valve is location on the
left rail, and relieves excessive fuel pressure which returns to the fuel tank.
Return System
The fuel return system routes fuel from the fuel injectors, the pressure relief valve, and the fuel injection pump. The return fuel travels to the fuel
cooler and then to the fuel tank. This fuel is used to cool and lubricate the injection pump and the injectors.
DIAGNOSTIC AIDS
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The fuel return volumes vary based on the American Petroleum Institute (API) rating of the diesel fuel.
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A fuel injector may have high fuel return flow only at higher engine temperatures.
CIRCUIT/SYSTEM VERIFICATION
With the engine running at idle the Actual Fuel Pressure should be close to the Desired Fuel Rail Pressure. During engine cranking the Actual Fuel
Pressure should be at least 10 MPa. Inspect the fuel return hoses and lines for external leaks or damage.
CIRCUIT/SYSTEM TESTING
IMPORTANT: If you were not referred to this test from another diagnostic, do not perform this procedure. Only perform this test when the fuel is
more than 18°C (65°F).
1. Remove the fuel pressure relief valve return hose and plug the hose to prevent fuel leakage.
2. Install a section of rubber fuel hose on the fuel pressure relief valve connection and place loose end of hose into a clean fuel container.
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If the engine cranks but does not start, crank engine for 15 seconds. Observe for fuel leaking from fuel pressure relief valve.
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If fuel leaks from the fuel pressure relief valve, replace the pressure relief valve.
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If the engine starts and runs, idle the engine while commanding the fuel rail pressure to 180 MPa with a scan tool. Observe for fuel leaking
from fuel pressure relief valve.
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If fuel leaks from the fuel pressure relief valve, replace the pressure relief valve.
3. Remove the fuel return hose from the fuel injectors of the right cylinder bank.
IMPORTANT: Always replace the fuel return hose retaining clips on the fuel injectors with new clips after removing.
4. Connect the yellow hoses from the J 45873 to the Fuel Injector Test Adapters.
5. Connect the Fuel Injector Test Adapters with yellow hoses to each fuel injector return port of the right cylinder bank, and install the retaining
clips.
6. Install the 4 yellow hoses in the J 45873 graduated cylinders in numerical order.
7. Connect the fuel return hoses to the J 45873-31 to prevent leakage.
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If the engine starts and runs, idle the engine until fuel start dripping into all the graduated cylinders and yellow hoses are full of fuel.
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If the engine does not start, crank the engine in 15-second intervals, with 1 minute cooling time between intervals, until fuel starts to flow into
all of the graduated cylinders.
IMPORTANT: The engine cranking speed must be more than 150 RPM during the cranking portion of this test.
8. Elevate the 4 yellow hoses to retain the fuel in the hoses, and empty the 4 graduated cylinders into a suitable container.
9. Install the 4 yellow hoses in the J 45873 graduated cylinders in numerical order.
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If the engine starts and runs, idle the engine for 15 seconds.
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If the engine does not start, crank the engine for 15 seconds.
10. Measure the quantity of fuel in each of the graduated cylinders.
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If high return flow was recorded, remove the fuel feed pipes from any fuel injectors that have high return flow and install the EN 47589 to the
fuel rail outlets.
11. Retest the fuel return flow, using the Fuel System Specifications, and cap any additional high return flow injectors.
