Leaking fuel injection pump

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    Rainshadow has the Perkins 4-108 still, and the fuel injection pump has just started leaking at the throttle control where the rod enters the pump. It is dripping about 1 drip per second, and this drip rate may be dependent on the throttle setting.

    Does anyone have advice for whether this pump can be rebuilt, or whether we should be looking for a replacement? Could this be some simple seal replacement? We are likely to hire the local diesel mechanic to do the work to ensure the timing is correct once the pump is reinstalled – but I’m wondering if anyone has words of advice for us? We are not experienced diesel mechanics, but always willing to learn.

    Thanks – Marilyn

    Happy Dolphin

    Yes, repair easy and cheap
    In at nutshell it needs new O-ring
    No need to remove pump from engine
    Disconnect throttle and stop cable completely from pump
    Remove two retaining bolts (may be star type heads) holding spindle unit/casting lift upwared carefully and remove unit taking care not to tear gasket
    The spindle will now pull out from casting revealing worn O-ring
    Replace and re assemble
    The casting gets worn oval by spindle and in severe cases needs replacing eventually
    Note absolute cleanliness is needed wash hands tools parts before you start and as you proceed (sorry in diesel or paraffin or petrol)

    Happy Dolphin

    oops you may need to remove manifold/heat exchanger for good access

    Happy Dolphin

    Oops again this is for hydraulic governed pump but if its mechanical governed very similar but you have to fiddle with governor spring to unhook it when top is unscrewed (nothing major)
    Most diesel mechanics will not strip a pump tho


    Hi Roy,

    Thanks for this advice – you inspired me to try it. I spent much of today cleaning the engine, draining the coolant, and removing the manifold. Fortunately, the previous owner stocked up on spare gaskets so we are set for replacing those.

    Now, I have good access to the pump – except there are two fuel lines that pass over it. Can you tell me about how much I’ll have to pull the spindle unit up? I think there is only about 3/4″ of space. Should I just disconnect and move the fuel lines?



    Happy Dolphin

    yes remove them from memnory it has to lift 3/4 inch

    Happy Dolphin

    from memory again if you remove just outer casting retaining bolt then i think spindle will then pull out spindle has groove cut in it to retain it when bolt is in


    Hi Roy, I owe you a beer (or three).

    Like I said before, you inspired me to have a go, and yesterday, I finally finished the repair, and everything works now! Really appreciate your help. I’ll write up some notes on the process and put that on our svrainshadow.com blog. The hardest part (besides overcoming my own stupidity) was finding a source for the O-rings. A diesel injection pump repair place mailed some to me, but the one for the stop control broke as I was installing it (I think it was defective). We had to drive to Pt Townsend (over an hour) to get a replacement – none of the local diesel shops, or auto parts shops had them in the right size. But, it all worked out in the end, so we’re happy.

    BTW, you are exactly correct about just removing the outer casting retaining bolt and being able to pull out the throttle spindle and replace the o-ring. But we figured we should replace the stop control spindle o-ring while we were at it.


    Happy Dolphin

    the stop control gets far less use but can get brittle with age
    here is another tip
    if its hard to start see if its injecting only a small amount of fuel if it is
    remove fuel inlet pipe
    remove the hexagon unit it was screwed into carefully
    remove small nylon filter
    remove the barrel under this very gently note position and way up of parts (only 3)
    using brasso or Tcut and two matches re lap small piston (this sticks causing poor fuel flow)
    as befor wash hands and parts and reassemble a touch of grease will hold bits in place
    this is another $1000 job about 1/2 hours work

    Happy Dolphin

    timing setting all diesels running at lowish revs or tick over out of gear, if smoke is white advance it if smoke is black retard it simple

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