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Diagnostic Test

  1. CHECKING FUEL PRESSURE 
    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. Turn the ignition off.
    2. Install the Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel) at the engine.
    3. Ignition on, engine not running.
    4. With a scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
      NOTE:

      Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).

      Choose a conclusion that best matches your fuel pressure reading.

      Below Specification 

      • Go To  2.

      Within Specification 

      • Go To  4.
  2. RESTRICTED FUEL SUPPLY LINE 
    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. Turn the ignition off.
    2. Remove the Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel).
    3. Raise the vehicle on a hoist, and disconnect the fuel pressure line at the fuel pump module.
    4. Install the Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel) between the fuel supply line and the fuel pump module.
    5. Ignition on, engine not running.
    6. With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge.
      NOTE:

      Fuel pressure specification is 407 kPa +/- 34 kPa (59 psi +/- 5 psi).

      Is the fuel pressure within specification?

      Yes 

      No 

      • Go To  3.
  3. CHECKING THE FUEL INLET STRAINER 
    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. Turn the ignition off.
    2. Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.

      Is the Fuel Inlet Strainer plugged?

      Yes 

      No 

  4. FUEL PUMP MODULE 
    NOTE:

    Before continuing visually and physically inspect the fuel delivery system for external leaks or damage. Repair/replace as necessary.

    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. Turn the ignition off.
    2. Install the Fuel Pressure Decay Tester (special tool #8978A, Decay Tool, Fuel) at the intake manifold.
    3. Start the engine and allow the fuel system to reach maximum pressure.
    4. Turn the ignition off.
    5. Close the Fuel System Isolation Valve and then wait 5 minutes before proceeding.
      NOTE:

      Fuel specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi).

    6. Read the Fuel Inlet and Fuel Outlet Pressure Gauges. The pressure should not drop more than 10 psi on either gauge.
    7. Monitor the fuel pressure gauge for a minimum of 5 minutes.

      Does the fuel pressure drop more than 10 psi?

      Yes - On Fuel Inlet Gauge 

      Yes - On Fuel Outlet Gauge 

      No 

      • If directed here by another test, return to that test. Otherwise, test complete.
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