Diagnostic Test

VISUALLY CHECK THE FUEL DELIVERY SYSTEM FOR LEAKS AND DAMAGE
WARNING:
The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting, or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
1. Visually inspect the fuel delivery system for external leaks, pinched or damaged fuel lines.
  Is the system leaking or damaged?
  
  Yes
  - Repair or replace as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to For 3.6L, refer to POWERTRAIN VERIFICATION TEST . For 5.7L, refer to POWERTRAIN VERIFICATION TEST . For 6.2L, refer to POWERTRAIN VERIFICATION TEST For 6.4L, refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 2
INSTALL APPROPRIATE FUEL LINE ADAPTERS/FITTING FROM THE GAS AND DIESEL FUEL PRESSURE/DECAY TESTER 8978A

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1. Turn the ignition off.
  WARNING:
  The fuel system is under a constant pressure (even with the engine off). Before testing or servicing any fuel system hose, fitting, or line, the fuel system pressure must be released. Failure to follow these instructions can result in possible serious or fatal injury.
2. Release the fuel system pressure. Refer to FUEL DELIVERY, GAS, STANDARD PROCEDURE .
3. Disconnect the fuel rail supply line connector at the fuel rail. Refer to FITTING, QUICK CONNECT, STANDARD PROCEDURE .
4. Install the appropriate Fuel Line Adapters/Fittings from the (special tool #8978A, Decay Tool, Fuel).
  Proceed
  - Go To 3
INSTALL THE FUEL PRESSURE GAUGE ASSEMBLY

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1. Connect the Fuel Decay tool gauges and bottle, with the Fuel Inlet Hose (1) toward the Fuel tank side and the Fuel Outlet Hose (2) toward the fuel rail side of the system.
2. Connect special tool Drain Extension Hose 535680 (3) to the Fuel Pressure Gauge Assembly Drain Hose (5).
3. Connect Reservoir Assembly 534960 (4) to Drain Extension Hose 535680 (3).
  WARNING:
  To reduce the risk of fire and possible serious or fatal injury, place Reservoir Assembly 534960 (4) on the floor and out of the way so that it is not a trip hazard.
  
  Proceed
  - Go To 4

CHECK THE FUEL PRESSURE TO THE FUEL RAIL AND ENGINE

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Perform the following procedure to purge air from the system:
- Open the Fuel System Isolation Valve (1).
- Close the Flow Test Valve (2).
- Ignition on, engine not running.
- With the scan tool, actuate the Fuel Pump.
- Open the Flow Test Valve (2) for 10 seconds, then close the Valve.
- CAUTION: Stop All Actuations.
- Turn the ignition off.
- Disconnect, empty and then reconnect the Reservoir Assembly.
While monitoring the pressure gauges, crank and start the engine (if engine will start).

This system is a variable pressure fuel system. Therefore the pressure can change during different modes of operation. Ambient temperature and fuel temperature can also contribute to fuel pressure changes. Use the table below for expected pressure reading during each mode of operation.

Mode of operation	Notes	Expected fuel pressure range
During cranking	During cranking the Fuel Pump is operated in an open loop Duty Cycle. The Duty Cycle is fixed and pressure should be static	Approximately 520 kPa (75.4 psi)
Engine running at idle	Fuel pressure can vary depending on ambient and fuel temperature. The pressure is raised during high ambient temperatures to prevent boiling of the fuel	Ranges between 340 kPa (49.3 psi) and 400 kPa (58 psi)
Normal operating range	Total operating range from idle to driving under load	Ranges between 340 kPa (49.3 psi) and 550 kPa (79.8 psi)
100% Duty Cycle	Maximum pressure is regulated by the pressure relief valve and can vary some between Fuel Pumps	Ranges between 600 kPa (87 psi) and 700 kPa (101.5 psi)

Read the Fuel Pressure Gauge (3) and record the reading.
Is the fuel pressure reading within the specifications in the table?

Yes
- Go To 6
No
- Go To 5

CHECK FUEL PUMP OPERATION
1. Turn the engine off.
2. Turn the ignition on, engine not running.
3. With a scan tool, actuate the Fuel System test.
  NOTE:
  It may be necessary to use a mechanics stethoscope in the next test step.
4. Listen for fuel pump operation at the Fuel Tank.
  Can you hear the Fuel Pump operating?
  
  Yes
  - Check for a restriction in the fuel lines between the Fuel Tank and Fuel rail. In no problems are found, replace the Fuel Pump Module in accordance with the Service Information
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to For 3.6L, refer to POWERTRAIN VERIFICATION TEST . For 5.7L, refer to POWERTRAIN VERIFICATION TEST . For 6.2L, refer to POWERTRAIN VERIFICATION TEST For 6.4L, refer to POWERTRAIN VERIFICATION TEST .
  No
  - If there are no Fuel Pump Control Module (FPCM) circuit DTCs present, replace the Fuel Pump Module in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to For 3.6L, refer to POWERTRAIN VERIFICATION TEST . For 5.7L, refer to POWERTRAIN VERIFICATION TEST . For 6.2L, refer to POWERTRAIN VERIFICATION TEST For 6.4L, refer to POWERTRAIN VERIFICATION TEST .
CHECK THE FUEL DELIVERY SYSTEM FOR LEAK DOWN

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1. Turn the engine off.
2. Close the Fuel System Isolation Valve (1) and monitor the Fuel Inlet (2) and Fuel Outlet (3) pressure gauges for five minutes. The pressure should not drop more than 10 psi on either gauge.
  Does the fuel pressure drop more than 10 psi on either gauge?
  
  Yes - On Fuel Inlet gauge (2)
  - Replace the Fuel Pump Module.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to For 3.6L, refer to POWERTRAIN VERIFICATION TEST . For 5.7L, refer to POWERTRAIN VERIFICATION TEST . For 6.2L, refer to POWERTRAIN VERIFICATION TEST For 6.4L, refer to POWERTRAIN VERIFICATION TEST .
  Yes - On Fuel Outlet gauge (3)
  - One or more of the Fuel Injectors is leaking. Replace the leaking Fuel Injector(s).
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to For 3.6L, refer to POWERTRAIN VERIFICATION TEST . For 5.7L, refer to POWERTRAIN VERIFICATION TEST . For 6.2L, refer to POWERTRAIN VERIFICATION TEST For 6.4L, refer to POWERTRAIN VERIFICATION TEST .
  No
  - If directed here by another test, return to that test. Otherwise, test complete.