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Home >> Jeep >> 2016 >> Grand Cherokee Laredo, AWD >> Repair and Diagnosis >> Engine Performance >> Fuel Delivery >> Fuel System >> Fuel Delivery, Diesel >> Standard Procedure >> Diesel Fuel System Contamination >> Diagnostic Test

Diagnostic Test

  1. CLEAN SIDE DIESEL FUEL SAMPLE COLLECTION AND INSPECTION 
    WARNING:

    Follow these safety precautions to reduce the risk of fire and possible serious or fatal injury when performing this test procedure.

    • Fuel or fuel vapors are highly flammable. A fire could occur if an ignition source is present. Do not expose the fuel or the test equipment used in this procedure to open flames or sparks.
    • Inhalation of fuel vapors could lead to disorientation and personal injury. Keep the service area well ventilated, or perform this test procedure in an area where there is a building exhaust removal system.
    • Relieve fuel system pressure before servicing fuel system components.
    • Use extreme caution when connecting and disconnecting fuel lines.
    • Considerable fuel leakage may occur when servicing the fuel system. Wear protective eyewear and clothing to protect from fuel splash, and take suitable fuel containment measures.
    • Wrap a shop towel around the fuel pressure gauge connection to absorb fuel leakage that occurs when connecting the test equipment. Place the towel in an approved container when complete.
    • Never store fuel in an open container due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby.
    • High-pressure fuel lines deliver diesel fuel under extreme pressure from the injection pump to the fuel injectors. This may be as high as 29, 008 psi (2000 bar). Use extreme caution when inspecting for high-pressure fuel leaks. Fuel under this amount of pressure can penetrate skin causing possible serious or fatal injury.
    NOTE:

    The photos in this test step illustrate the steps in this test procedure for clarification.

    NOTE:

    The fuel filter MUST NOT be removed or replaced prior to taking sample in order to get accurate results.

    NOTE:

    Warm the engine before collecting the fuel sample.

    Start the engine and run until it reaches normal operating temperature.

    Fig 1: Tilting Measuring Cup & Positioning Flashlight On Bottom Of Cup
    GC0143984Courtesy of CHRYSLER GROUP, LLC
    1 LED FLASHLIGHT
    2 MEASURING CUP
    3 SLOWLY TILT THE CUP TOWARD YOU
    1. While the engine is warming up, clean the clear tubing with clean diesel fuel and the glass measuring cup using brake clean and compressed air only. Do not use a towel.
      NOTE:

      Do not use brake clean or other chemicals on any vehicle parts for the fuel handling system such as lines, pumps or fittings.

    2. Turn the engine off.
      Fig 2: High Pressure Pump Blocker Shield & Bolts
      GC0146780Courtesy of CHRYSLER GROUP, LLC
    3. Remove the bolts (2) and fuel injection pump blocker plate (2).
    4. Disconnect the low pressure supply line quick disconnect fitting (2) from the fuel injection pump.
    5. Cap off the male fitting on the fuel injection pump supply line that was disconnected.
    6. Install the Fuel Decay Tool 8978A with the necessary adapter hose(s). (special tool #8978A, Decay Tool, Fuel)
    7. Cycle the ignition to obtain a fuel sample in the reservoir with out starting the engine.
    8. Pour approximately 1/4 inch of diesel fuel in the measuring cup and allow the sample to sit for 10 minutes in a dust free environment to allow the debris to settle to the bottom. It is important to not allow any air born contaminates to get into the fuel sample. Do not shake, swirl, or agitate the fuel in any way. The contamination should settle to the bottom. 
      Fig 3: Locating Fuel Contamination In Measuring Cup
      GC0143986Courtesy of CHRYSLER GROUP, LLC
      1 Contamination will gather at the trailing edge of fuel.
      VIEW CAREFULLY, LOOKING FOR VERY SMALL PARTICULATE MATTER (May Look Cloudy)
      NOTE:

      Follow these next steps exactly to inspect the sample for contamination.

    9. Hold the measuring cup by the handle in one hand and shine the LED flashlight through the bottom of the container toward the handle of the cup.
    10. Slowly tilt the measuring cup toward you and keep the LED flashlight at the trailing edge (1)  of the fuel as it comes down the bottom of the cup and inspect for contamination.
      • Any dirt in the fuel will collect and be pulled by this trailing edge of fuel (Number one in the last figure)  . It may be any color and sometimes looks as though the fuel is cloudy This is the contamination  .
      • If you see ANYTHING AT ALL  , the fuel is contaminated.

      Is the fuel sample contaminated?

      Yes 

      • To ensure that the In Tank Lift Pump is operating properly, perform the Lift Pump Flow Test. For instruction and specifications on this procedure, refer to the CHECKING THE FUEL DELIVERY SYSTEM procedure, test step 5. After checking the In Tank Lift Pump operation, perform the DIESEL FUEL SYSTEM CLEANING PROCEDURE. Refer to STANDARD PROCEDURE  .
      • Go To  2

      No 

      • Install NEW  fuel filter and Mopar (CRC) fuel injector cleaner into the fuel tank at a ratio four times the recommend concentration.
      • Go To  2
  2. DIAGNOSTIC PATH 

    Were you instructed to inspect for Fuel Contamination from the MIL LIGHT ON PRETEST PROCEDURE?

    Yes 

    • Perform the diagnostic trouble code test that was found to be present. Refer to the DTC INDEX article.

    No 

    • Go To  3
  3. DIAGNOSTIC PATH CONTINUED 

    Were you instructed to inspect for Fuel Contamination from a Non-DTC TEST PROCEDURE?

    Yes 

    • Perform the DIESEL AFTERTREATMENT VALIDATION. Refer to the appropriate Diagnostics & Testing article in Engine Performance .

    No 

    • Return to Diagnostic Test that directed you to inspect for fuel contamination.
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