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Thread: D3b fuel problem

  1. #1
    Join Date
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    long island NY, Hancock Ma
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    Default D3b fuel problem

    My D3B--27Y03729 starves for fuel after about 1/2 hour run time, it starts at 30 psi fuel pressure and then slowly dies down to 0 and then starts missing--lower the throttle and it goes up to 10 psi. shut it of,wait 15 minutes and start it and 30 psi.

    I have installed new fuel filters, cleaned the screen in the banjo fitting at the transfer pump, blown the line out from the transfer pump to the fuel tank and fuel flow under gravity is fine, I have hooked up a fuel pump to a hose and sucked about 5 gallons out of the tank bottom and it was all clean.I also removed the fill cap to see if venting is a problem.

    the parts diagram for the fuel tank shows two valves at the bottom. one a drain and the other needle valve for fuel supply. I also observed a second line going to the tank bottom with no valve. The parts diagram also shows a screen in the tank, with a part number, and after some research it screens fuel for the drain valve,of which i don't understand--also there is no plate on the bottom of the tank to gain access to this screen.
    appreciate any opinions on this.
    d3b fuel tank.gif
    Cat 941B, Cat D2 4U, Cat D3B, Cat D4 7U, Cat D6 9U

  2. #2
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    Default

    Sounds like the fuel cap causing vacuum.

  3. #3
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    Corralitos, Ca.
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    Default

    What's the engine s/n?

  4. #4
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    Default

    The D3B's often have a small in-line filter (Metal shiny thing) clipped in to the feed hose just before the lift pump, I would look here for trouble first. tctractors

  5. #5
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    This arrangement as described has a return line to the fuel tank. Looks like there is a back pressure or pressure relief valve located in the support under the fuel injection pump. I suspect there is a problem with the valve, probably some crud holding it open and draining off your fuel pressure back to the fuel tank. The engine s/n would verify the arrangement.

  6. #6
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    the machine arrangement is 5G1093---the engine number is 45V51332, arrangement 2W7487

    as I stated in my first post i have run the machine with the fuel cap off and have cleaned out that screen on the transfer pump inlet line, all to no help

    if the fuel pressure relief valve is stuck open why would i read 30 psi at start up and after 15 min shutdown when hot??--

    found this double fuel line schematic on the online parts diagram
    D3B fuel lines.gif
    Last edited by dpendzic; 10-14-2017 at 08:23 AM.
    Cat 941B, Cat D2 4U, Cat D3B, Cat D4 7U, Cat D6 9U

  7. #7
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    Oklahoma
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    Quote Originally Posted by Rome K/G View Post
    Sounds like the fuel cap causing vacuum.
    This^^^^^^^ exactly the same thing happened to me once make sure the vent in the fuel cap is open

  8. #8
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    Quote Originally Posted by dpendzic View Post
    the machine arrangement is 5G1093---the engine number is 45V51332, arrangement 2W7487

    as I stated in my first post i have run the machine with the fuel cap off and have cleaned out that screen on the transfer pump inlet line, all to no help

    if the fuel pressure relief valve is stuck open why would i read 30 psi at start up and after 15 min shutdown when hot??--

    found this double fuel line schematic on the online parts diagram
    D3B fuel lines.gif
    Because the valve is not stuck open. It is not shutting off completely due to a seating problem. There apparently is enough fuel to start and for light load but drops off as demand increases. The valve is shown in section A -A. The parts book does not do a very good job of showing the lines configuration.
    Did you check the screen in the inlet to the transfer pump?
    I can't tell from the parts book if that relief valve is a local recirculating type or recirculates back to the tank. I'm just assuming it goes back to the tank because of the return line. Anybody know for sure?
    Attached Images Attached Images
    Last edited by Old Magnet; 10-14-2017 at 11:07 AM.

  9. #9
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    Quote Originally Posted by captainhowdy View Post
    This^^^^^^^ exactly the same thing happened to me once make sure the vent in the fuel cap is open
    oops sorry was skimming again and missed the part where you ran with the cap off

  10. #10
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    Check those fuel lines from the tank to the pump if there is a pinhole wore through from rubbing on something.

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