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NJ 4M40T fuel pump issue

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  • NJ 4M40T fuel pump issue

    Hi Everyone
    I have a typical 4M40T fuelling issue with worn seals in the fuel pump
    Has anyone tried bypassing the injector/fuel pump permanently with an inline electric pump from the tank line direct to the filter?
    Seems like an easy way out to me, maybe too easy?

    However, by side stepping the fuel pump and it therefore running dry, will it be destroyed? (I assume the diesel acts as a fuel pump lube also)

    Alternately, would it be possible to use an in-tank filter instead, running the engine bay tank line direct to the filter and again bypassing the injector/fuel pump altogether
    You'd have the issue of a dry fuel pump though
    All advise welcome

    Thanks guys
    Mario

  • #2
    The fuel pump is also the timing for the motor so an electric pump won't work. The only real answer is to spend the money and repair the pump
    Current vehicles: 1995 3.5l nj Pajero x 2, 1995 2.8td Mitsubishi Delica,2011 Jeep Patriot, 2 x 1971 ta 22 celicas, 74 ta 22 celica, ke 35 corollla with 18rg, 95 gtr 1000, 79 leyland terrier bus ( 350 chev),1978 ke 35 corolla, 1980 ra 40 celica 18rgeu,2011 agricat jd495
    Currently wrecking nh gls lwb, nh gl pov pack, 2 x nj gls lwb nl lwb, NH glx manual, 92 L300 delica

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    • #3
      Agreed!
      Our motor is fully mechanical, no electronic gimmicks.
      If the pump leaks get a seal kit and fix it, sorry only option apart from buying a replacement pump.
      '94 2.8TD, 2" lift, low mount winch, bullbar, roofrack, UHF, custom drawers, HID spotties, cam, GPS....
      Password for all my files: downunder

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      • #4
        Agreed x2!
        The mechanical pump serves a couple of purposes:
        a) It controls injector timing
        b) It acts as your throttle
        c) It generates fuel pressure far higher than most 12v electric pumps could manage, especially by the time it is forced through a high volume/low pressure filter.
        d) It references boost pressure to control fuelling

        And yes, the fuel lubricates the pump and injectors...
        2001 NM 2.8TD GLS Pajero, ARB bar, 9000lb Tmax winch, Airtec snorkel, GME UHF, breathers, 265/75 Goodyear Wrangler Duratracs, rear storage, Ebay HID's, King EHD lift, LED lighting, dual battery kit, bushskinz intercooler/sump guards, narva +120 globes, tigerz awning, Exedy HD SMF clutch/flywheel kit, pinstriping aplenty...

        To do list: Locker, sliders, transmission guard, blah blah blah....

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        • #5
          But the injector pump has 2 seperate functions, 1 is a lift pump, to draw fuel from the tank
          The 2nd is to take fuel from the filter and direct to the injector pump and on to the injectors
          I know the car will run if the tank line is connected direct to an inline filter and on to the injector pump, bypassing the fuel pump altogether. The injector pump has enough suction to draw the fuel from the tank. Why cant I place an inline electric pump from the tank to the main filter instead?

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          • #6
            I think you'll find even if it was possible ....the availability of pumps that can be used for diesel would be very rare

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            • #7
              it sounds like what you are trying to do is bypass the lift pump if so you are asking for trouble and it will cost you a motor. The shonkies who put an inline pump in to mask a failing fuel pump know that it will last a little while so it is no longer there problem.

              By passing the lift pump in the manner you describestill leave the main pump in play but allows fuel to be pushed past the seals in the pump into your sump and eventually causes a fault called diesel run on. Do a search on it and see what happens to motors that have this happen.
              Current vehicles: 1995 3.5l nj Pajero x 2, 1995 2.8td Mitsubishi Delica,2011 Jeep Patriot, 2 x 1971 ta 22 celicas, 74 ta 22 celica, ke 35 corollla with 18rg, 95 gtr 1000, 79 leyland terrier bus ( 350 chev),1978 ke 35 corolla, 1980 ra 40 celica 18rgeu,2011 agricat jd495
              Currently wrecking nh gls lwb, nh gl pov pack, 2 x nj gls lwb nl lwb, NH glx manual, 92 L300 delica

              Comment


              • #8
                Couldn't agree more.
                Theory is one thing, practical use a whole different story!
                Consider this:
                Taking the pump off and replacing all vital seals will cost you about 100 bucks for the kit (cheaper on Ebay).
                One nice afternoon in the sun should be enough to fix it.
                Sure it is a messy job and can be quite tricky to keep the timing - but that where waterproof whit markers come to play
                On the other hand, bypassing the main pump would require to modify the existing pump - without taking it out not a good idea, so a seal kit would be needed anyway.
                And as said: the internal pump is controlled, an external won't be!
                Continous overpressure will cause all sorts of failure up to the mentioned wrecked engine.
                The price for a proper pressure pump suited for continous use on diesel will cost you more that getting the pump fixed by a mechanic
                '94 2.8TD, 2" lift, low mount winch, bullbar, roofrack, UHF, custom drawers, HID spotties, cam, GPS....
                Password for all my files: downunder

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                • #9
                  Well thanks guys, you've convinced me to get it done properly. Think i'll go for a pump rebuild not just a seal kit.

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