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2.5NA in a Series 3, uncontrollable max rpm!!

Discussion in '2.5 N/A' started by Adam Cruickshank, Jan 12, 2018.

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  1. Adam Cruickshank

    Adam Cruickshank New Member

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    Hey folks,

    I am working on finishing up an install of the 2.5NA into my Series 3...

    I rebuilt the engine about 3 years ago and it had not run for an uncertain number of years prior to that but I've estimated 6-10 years since the engine was last run.

    My current issue is when I fire up the engine, it goes right to max rpm. I can keep the rpm down by almost completely blocking off the intake.. Pulling the wire of the stop solenoid stops the running immediately as it should.

    My current theory is that the mechanism inside the injection pump (IP) is stuck at the wide open throttle (WOT) position (I held the throttle wide open while bleeding). The exterior of the pump looks great, nice and clean but I have no idea what the inside looks like and can speculate that it is corroded from sitting for so long...

    Thoughts on my theory, other possible causes, or ways to confirm/fix the problem?

    I am thinking of removing the top cover of the IP to have a look at the bits I can see from there... I have reviewed the threads I could find (including some photos) regarding the top cover removal and feel comfortable with the scope of work involved.

    Thanks in advance!
     
  2. Huddy84

    Huddy84 Active Member

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    I think u might be right, either gummed up or corroded due to lack of use. Mine was done by a diesel specialist but hopefully a clean out may get it going.

    Lol, people usually have the opposite problem and can’t get it running.
     
  3. Adam Cruickshank

    Adam Cruickshank New Member

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    Thanks for the reply Huddy84, you can imagine my surprise when the first time it lights up after sitting for sometime (3-4 years since rebuild) it goes to full throttle! Good thing is that there was a pile of cranking trying to bleed the fuel system so engine oil was circulated to the important bits.. not a dry start at full throttle!

    Are there any schematics/repair manual for the IP out there? I have had little success finding a working file online..
     
  4. Huddy84

    Huddy84 Active Member

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    I’ve only seen odd posts in this section. I think taking them too far apart requires specialist tools and testing equipment. Fortunately I have a spare so any issues I’d swap em and get the broken one refurbed. Sorry that’s not much help.
     
  5. Blackburn

    Blackburn Well-Known Member

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    The tickover is set by the spindle nearest front of pump it is not jammed open ?
    Some info I collected when I had a 2.5 fitted.
     

    Attached Files:

  6. Adam Cruickshank

    Adam Cruickshank New Member

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    That's good info, thanks Blackburn! I remember seeing that same image while searching for info.

    I have already backed off the idle speed stop and the throttle stop, neither one made a difference... seems I am stuck at max throttle regardless of exterior inputs / settings.

    Huddy84, I have no plans to completely disassemble but I have seen posts along with photos that involve pulling the top cover only. Assuming what ever meters the fuel is stuck at a high rpm position I am uncertain if I will see anything to indicate the problem by removing the top cover..

    I do have a spare but it has been sitting just as long under similar conditions... perhaps sending it off to the specialist is my best option at this point. Now, to see if I can find a specialist in my area that can work on this pump... they are not very common over here!
     
  7. Huddy84

    Huddy84 Active Member

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    I bet not. If the throttle is jammed, what are the chances other bits in the pump aren’t working at their best. If your going to the effort to take it off you might as well make sure it’s pukka before putting it all back together.
     
  8. Blackburn

    Blackburn Well-Known Member

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  9. Adam Cruickshank

    Adam Cruickshank New Member

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    Definitely a very good point that I have been considering. May end up sending my spare for overhaul and being done with it! If I do that, I may pull the top cover just for info/experience..



    I do recall seeing that image as well! Thank you for the info, I will have a look at the link.
     
  10. Chase

    Chase New Member

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    Adam,
    Did you get this sorted yet?
    C
     
  11. Adam Cruickshank

    Adam Cruickshank New Member

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    I haven't yet. I have a number of other things to work on so I am letting it sit full of fuel... I am optimistic but not hopefull that it will sort itself out!

    A friend up the road had the same thing happen on an old tractor with the DPA pump and was able to sort it with a bit of wd-40 while working the mechanism once the top cover was removed... that will most likely be the next step.

    In the meantime, I have been spending a pile of time sorting wiring and repairing/prepping more bits for the galv tank!
     
  12. Turboman

    Turboman Rural Activist

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    I take it you have checked the external linkages, or the throttle cable, aren't sticking in the full flow position?

    If it is the pump, you are probably on the right track with the professional rebuild.

    In the short term, you could try cleaning the pump internals with petrol (gasoline). Remove the fuel filter, and fill it with petrol. Then start up, and let th pump draw in the petrol. Stop the engine when you think the petrol will have been drawn into the injector pump, and then leave it for a bit, and try again.
     
  13. Adam Cruickshank

    Adam Cruickshank New Member

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    The issue is undoubtedly internal to the pump. I plan to remove the top cover before considering a professional rebuild.

    I may attempt the petrol cleaning as described before removing the cover.
     
    Turboman likes this.
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