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  • P0304 Cylinder #4 Misfire

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    Mopar1973Man

    P0304 CYLINDER # 4 MISFIRE

    When Monitored and Set Condition:

    When Monitored: While the engine is idling.
    Set Condition: Misfire detected on multiple cylinders.

    POSSIBLE CAUSES

    • LOW FUEL
    • OTHER DTC'S
    • DAMAGED FUEL LINES
    • VALVE TRAIN
    • OBSTRUCTED FUEL INJECTOR SUPPLY LINES
    • DAMAGED OR OBSTRUCTED HIGH PRESSURE CONNECTORS
    • EXTERNAL DAMAGED FUEL INJECTORS
    • INTERNAL DAMAGED FUEL INJECTOR
    • NO COMPRESSION
    • EXCESSIVE ENGINE LEAK DOWN

    DIAGNOSTIC PROCEDURE

    NOTE: Refer to VERIFICATION TESTS for appropriate verification test procedures.

    1. Using the DRBIII®, verify that the fuel level is above 15%. Is the fuel level above 15%?
      Yes --> Go To 2
      No --> Add fuel go to step 2. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    2. Read the Freeze frame data. Is the DTC equal to the freeze frame DTC?
      Yes --> Go To 3
      No --> Repair any other DTC's first. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    3. Visually inspect the injector supply lines for damage. Do you have any kinked or bent fuel lines?
      Yes --> Repair or replace damaged fuel lines. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 4
    4. Visually inspect the valve train and check the valve lash on the suspect cylinders. Is the valve train functional and the lash within the specifications listed in the service information?
      Yes --> Go To 5
      No --> Adjust the lash or fix or repair any damaged component(s). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    5. Remove the fuel injector supply lines for the suspect cylinders. Inspect both ends of the fuel injector supply lines for damage. Using shop air pressure, blow out the fuel injector supply lines to verify that they are not obstructed. Are the fuel lines free of debris or damage?
      Yes --> Go To 6
      No --> Replace the damaged or obstructed fuel injector supply lines. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    6. Remove the high pressure connectors for the suspect cylinders. Inspect both ends of the high pressure connectors for signs of damage. Using shop air pressure, blow out the high pressure connectors to verify that they are not obstructed. Are the high pressure connectors free of debris or damage?
      Yes --> Go To 7
      No --> Replace the damaged or obstructed high pressure connectors. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    7. Remove the suspect fuel injectors. Are the fuel injectors damaged?
      Yes --> Replace the external damaged fuel injectors & high pressure connectors. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 8
    8. With the DRBIII®, erase DTCs. Switch the misfiring injectors & high pressure connectors with injectors & high pressure connectors from cylinders that are firing properly. Operate the vehicle. Did the misfire DTC follow the suspect injectors & high pressure connectors?
      Yes --> Replace the internal damaged fuel injector and high pressure connector. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 9
    9. Perform engine compression test Did the suspect cylinders pass the compression test?
      Yes --> Go To 10
      No --> Repair the internal damage to the engine. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
    10. Perform engine leak down test Did the suspect cylinders pass the leak down test?
      Yes --> Test Complete.
      No --> Repair the internal damage to the engine. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

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