Avalanche 1500 2WD V8-5.3L (2008)
Reducing the internal temperature of the fuel tank results in lower evaporative emissions.
The fuel tank stores the fuel supply. An electric turbine style fuel pump attaches to the fuel pump module inside the fuel tank. The fuel pump supplies
high pressure fuel through the fuel filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is
needed by the fuel injection system. The fuel pump also supplies fuel to a venturi pump located on the bottom of the fuel pump module. The function of
the venturi pump is to fill the fuel pump module reservoir. The fuel pressure regulator, a part of the fuel pump module, maintains the correct fuel
pressure to the fuel injection system. The fuel pump module contains a reverse flow check valve. The check valve and the fuel pressure regulator
maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.
Special Tools
^
CH-48027 Digital Pressure Gage
^
J 37287 Fuel Line Shut-off Adapter
Circuit/System Verification
Important:
*
Repair all fuel system related DTCs before performing this diagnostic
*
Inspect the fuel system for damage or external leaks before proceeding.
*
Verify that adequate fuel is in the fuel tank before proceeding.
*
The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
*
Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.
1. Ignition OFF, all accessories OFF, install a CH-48027.
2. Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 345-414 kPa (50-60 psi) and
does not decrease more than 34 kPa (5 psi) in 1 minute.
Circuit/System Testing
Important:
*
The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
*
DO NOT start the engine.
Ignition ON, engine OFF, command the fuel pump relay ON with a scan tool and observe the fuel pressure gage while the fuel pump is operating.
Verify the fuel pressure is between 345-414 kPa (50-60 psi).
^
If the fuel pressure is greater than the specified range, replace the fuel pump module.
^
If the fuel pressure is less than the specified range, test, inspect, and repair the items listed below. If all items test normal, replace the fuel
pump module.
*
Restricted fuel feed pipe
*
Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
1. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
^
If the fuel pressure decreases more than the specified value, perform the following procedure:
1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (With CH 48027) Fuel Pressure Relief (Without CH 48027).
2. Install the J 37287 between the fuel feed pipe and the fuel rail.
3. Open the valve on the J 37287.
4. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the CH-48027.
5. Command the fuel pump relay ON and then OFF with a scan tool.
6. Close the valve on the J 37287.
7. Monitor the fuel pressure for 1 minute.
^
If the fuel pressure decreases more than 34 kPa (5 psi) within the specified time, locate and replace the leaking fuel injector(s).
^
If the fuel pressure does not decrease more than 34 kPa (5 psi) within the specified time, replace the fuel pump module.
2. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.
^
If the fuel pressure decreases more than the specified value, replace the fuel pump module.
