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Thread: D6 9U3405 Fuel Transfer Pump and Injection Pumps Questions

  1. #1
    Join Date
    May 2007
    Ava Il.

    Default D6 9U3405 Fuel Transfer Pump and Injection Pumps Questions

    I have some questions on my transfer fuel pump . What kind of pressure should I have when starting and how much will it change when running ? Also does this pressure affect the injection pumps? What kind of pressure should there be out of injection pumps? I just converted from pony to electric start. What should the engine compression be .


  2. #2
    Join Date
    Nov 2006
    Faunsdale, AL USA


    Usually if you have any pressure indicated on the CAT fuel pressure gauge during cranking it will start and pressure will come up a lot. At least enough to tell if filters are plugged etc. I think the low edge of the green band on the gauge is something like 12 psi. I think Eddie B has posted a service bulletin that detailed the differences between the old and new style gauges and the pressures they indicate.

    Injection pump pressure must exceed injector cracking pressure which is about 425 psi for the disposable capsule type though they will still work if a little lower. The older high pressure injectors crack at about 1350 psi and are supplied by similar pumps, so I doubt it is a pump problem very often. They can stick and not return to make a second stroke or stroke just fine but leak into the injection pump housing tray and out onto the ground through the drain line at the left front corner of the engine block. in between those two extremes, they will probably work.

    Eddie (eddieb )also posted some compression information though CAT did not encourage the use of that test. The recommended method was a leak down test using compressed air.
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

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