losing fuel pressure on my 2011 DD15 Cascadia

Discussion in 'Freightliner Forum' started by sandman608, Mar 30, 2014.

  1. Stealthy4

    Stealthy4 Bobtail Member

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    Jun 3, 2014
    0
    Was this issue ever fixed?

    Losing prime in the DD series of engines can be related to a few things, most likely an air leak in the system allowing the fuel to drain back to the tanks causing hard start. The hard part is finding the leak. The easiest way to do this is to narrow down the leak path to either the engine side or chassis side. To do this, have you tech perform a low pressure leak down test on the engine side fuel system.

    This involves installing a regulated air source (~70psi) to the inlet of the on-engine filter module and pushing air though the system so as to remove as much fuel from the system as possible. After a few minutes purge time stop the air purge and cap the outlet of the on-engine fuel module. Turn the air back on to pressurize the engine fuel system with ~70psi air. It should be mentioned that the air hose "device" should have a regulator, pressure gauge, and a shutoff valve that doesnt leak on it. (theres an actual service tool for this J-48710) This should only take a few seconds to hit pressure. Once pressure is achieve, close the inlet shutoff valve and monitor the pressure on the gauge. The pressure should read steady at 70psi. If it bleeds down over the next few minutes (20), you have a leak on the engine side fuel system. Two things can happen....if the pressure bleeds down to ~60psi and STOPS, you have high pressure fuel side leak. If it continues to leak down below 60psi, you have a low pressure side leak. If the pressure holds steady at 70psi, you do not have a leak on the engine side of the fuel system. This indicated you probably have a leak on the chassis side. Common places to check for leaks on the chassis side:
    1) Module inlet and outlet connections
    2) Frame mount filter connections
    3) Fuel tank shut off valves/equiflow valves mounted to the top of the transmission
    4) connection points at the fuel tanks
     
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  3. Smithmatch

    Smithmatch Bobtail Member

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    2
    May 10, 2014
    0
    I would check the low pressure and high pressure readings first.
     
  4. Bill8220

    Bill8220 Bobtail Member

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    Aug 26, 2014
    CARLSBAD NM
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    If you have a globe fuel filter remove inlet fuel line and fitting and check plastic ball check valve.
     
  5. RSQ20

    RSQ20 Medium Load Member

    I would have been all over this system with a smoke injector, if you have a leak the smoke would escape..

    +/-7psi would be enough, and a bright flashlight, not brain science.

    ... Philip
     
    77fib77 Thanks this.
  6. Jeremy Meek

    Jeremy Meek Bobtail Member

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    4
    Feb 25, 2015
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    I'm having the same trouble and the fuel drains out of the filter housing to the tanks right away. At first I would pressurize the tanks to get it going now I just shut the fuel off when I turn it off otherwise it won't start. I'm waiting on a fuel check valve for a week now due to lack of ordering and a wrong part order. Hopefully that solves the problem.
     
  7. mhyn

    mhyn Road Train Member

    4,255
    4,502
    Dec 29, 2008
    Northridge, CA
    0
    did you fix the problem ? what part was faulty ?
     
  8. Jeremy Meek

    Jeremy Meek Bobtail Member

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    4
    Feb 25, 2015
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    I changed the check valve on the small initial filter housing and that seems to have cured the no start while sitting overnight. It takes more cranking than it used to and I was told there is 2 other check valves in there for injectors and something else. Within guidelines of a 10 sec start but going to see how it goes over the next weekend. Did a air fuel pressure test from tanks to engine was ok.
     
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  9. Jeremy Meek

    Jeremy Meek Bobtail Member

    5
    4
    Feb 25, 2015
    0
    Well it all went for #### a few days later and gave me more trouble so I toughed it out for awhile till the job was done and we changed 2 more check valves and there was a third which we did not. It took a day or so of hard starts and working the air out but it came around and starts like new. Once I tried starting it before the prestart did its full cycle and it threw up an engine error and would not start till I got the code cleared and forced fuel up but its been good since.
     
  10. mhyn

    mhyn Road Train Member

    4,255
    4,502
    Dec 29, 2008
    Northridge, CA
    0
    2 more check valves ? are they located on high pressure pump ?
     
  11. Jeremy Meek

    Jeremy Meek Bobtail Member

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    4
    Feb 25, 2015
    0
    I wasnt around for a week when they came in but there was talk of injector check valve and a return check valve which could be the silver screw with the Allen bit on the side in front of the filters where the brown fuel lines are the third was to be one in the back of the fuel system but they could not really figure where that one went so we gave it back. I'll have to ask the mechanic and maybe get a couple location pictures.
     
    mhyn Thanks this.
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