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HOMESERVICE MANUALSJEEP2008COMMANDER OVERLAND, 4WDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMELECTRICAL DIAGNOSTIC TESTS*HARD START (FUEL SYSTEM)DIAGNOSTIC TEST
2008 Jeep Commander Overland, 4WD

Diagnostic Test

2008 Jeep Commander Overland, 4WDSECTION 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 personal injury or death.

    Turn the ignition off.

    Install a fuel pressure gauge at the engine.

    Ignition on, engine not running.

    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 

    1. Go To step  2.

    Within Specification 

    1. Go To step  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 personal injury or death.

    Turn the ignition off.

    Raise vehicle on hoist, and disconnect the fuel supply line at the fuel pump module.

    Install special tool #6539 (5/16") #6631(3/8") fuel line adapter and the fuel pressure gauge between the fuel supply line and the fuel pump module.

    Ignition on, engine not running.

    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 

    1. Visually and physically inspect the fuel supply lines between the fuel tank and the fuel rail. Repair/replace as necessary.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Go To step  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 personal injury or death.

    Turn the ignition off.

    Remove the Fuel Pump Module and inspect the Fuel Inlet Strainer.

    Is the Fuel Inlet Strainer plugged? 

    Yes 

    1. Replace the Fuel Pump Inlet Strainer.
    2. Perform POWERTRAIN VERIFICATION TEST .

    No 

    1. Replace the Fuel Pump Module.
    2. Perform POWERTRAIN VERIFICATION TEST .
  4. FUEL PUMP MODULE 
    NOTE: Before continuing visually and physically inspect the fuel delivery system for external leaks or damage. Repair/replace as necessary.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.