DD15 Engine

Section 5.1 External and Internal Low Pressure Fuel Leaks

Section 5.1
External and Internal Low Pressure Fuel Leaks

This condition will exist if there is an external or internal leak of the low pressure fuel system. Tool J-48710 is required for this testing.‪

Test as follows:‪

  1. Remove the fuel feed and return lines from the fuel filter module.
  2. Install J-48710 fuel pressure test kit onto the module.
    Click to see this graphic in a separate window
  3. Insure the shutoff valve is in the OFF position.
  4. Turn regulator counter-clockwise until it stops. The regulator is now set to zero pressure.
  5. Connect to shop air pressure.
  6. Turn the shutoff valve to the ON position.
  7. Turn the regulator clockwise to increase pressure in the fuel system to 30psi.
  8. Once the system pressure has reached 30 psi, let the system pressure stabilize for one minute then turn the shutoff valve to the OFF position and disconnect shop air from the regulator.

    Note: The fuel cooler and feed line for the amplifier circuit is located behind the fuel filter module. Ensure this area is not overlooked.

    Note: When releasing air pressure from the tool and fuel system, point the nozzle connection away from your body and into a container before opening the valve.

  9. Wait 30 minutes, then check the pressure. The system pressure should not drop over 30 minutes.
    1. If the pressure does not drop (still 30 psi), there are no low pressure fuel leaks. Continue troubleshooting elsewhere.
    2. If the system pressure drops off over 30 minutes, go to the next step.
  10. Reconnect shop air and turn on the valve.
  11. Use a soapy solution and spray all connectors, fittings, and braided hoses.
    1. If no leaks are found, go to next step.
    2. If leaks are found, repair as necessary.
  12. Remove oil fill cap and listen for internal air leaks.
    1. If internal leaks are heard, remove the rocker cover to locate where the leak is coming from, injector/pump.
    2. If no internal leaks are located, go to next steps
  13. Install cooling system pressure testing tool.
    1. If cooling system pressure increases and there is fuel in the coolant, replace fuel cooler located behind fuel filter module.
    2. If cooling system pressure does not increase, return to step 11 and retest. If no problem is found, verify repairs.


DD15 Fuel System Technician's Guide - DDC-SVC-MAN-0037
Generated on 10-13-2008

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