Need help with Primus No 51

Discussion in 'Stove Forum' started by Ralph Vartabedian, Oct 9, 2024.

  1. Ralph Vartabedian United States

    Offline
    Joined:
    Oct 8, 2024
    Messages:
    3
    Location:
    USA
    Hello,
    I am trying to restore a Primus 51 that I have had for years. The pump meets a lot of resistance when I try to pressurize the tank. I am familiar with other pressurized camp stoves. Is there a check valve at the end of the pump tube that could be a problem? The leather cup on the pump shaft looks like it is in good condition. When I pump it, a small amount of air enters the tank, but not enough to get much fuel coming out of the orifice and I have to constantly pump to keep the flow going. I put Coleman fuel in the spirit cup and heated up the fuel tubes. It should have fired up in there was enough pressure in the tank, right? Any advice? Thank you.
    upload_2024-10-9_11-48-48.jpeg
     
  2. ROBBO55

    ROBBO55 Subscriber

    Offline
    Joined:
    Oct 27, 2014
    Messages:
    2,310
    Location:
    Somersby, New South Wales, Australia
    Welcome to CCS @Ralph Vartabedian

    There's a non return valve (NRV) at the bottom of the pump tube. It's a spring loaded rubber PIP. Poking a wire down the hole may free up the moving parts but the PIP may have hardened with age and the NRV will need rebuilding.
    Search the site for NRV and there is plenty of info.


    upload_2024-10-10_6-6-59.jpeg
     
  3. Blackdog

    Blackdog United Kingdom SotM Winner Subscriber

    Offline
    Joined:
    Jan 7, 2009
    Messages:
    2,402
    Location:
    England
    There is a valve at the end of the pump tube- the non-return valve, abbreviated to NRV on this forum. It has a rubber seal, often called the 'pip', which may have stuck, causing excessive resistance. Equally old fuel deposits may be causing the NRV to stick. You can try soaking the valve in light oil or a penetrating oil of your choice, and poking a length of wire through the hole in the NRV body at the bottom of the pump tube, which may physically free it.

    There is a good chance the rubber pip will have degraded and will no longer provide an adequate seal. In order to replace it, the NRV needs removing and dismantling. Search for 'NRV tool' to see what you need to buy or make.

    Another cause of pressure loss is the filler cap seal, which may well need replacing.
     
  4. Ralph Vartabedian United States

    Offline
    Joined:
    Oct 8, 2024
    Messages:
    3
    Location:
    USA
    I'm pretty sure the filler cap is not leaking. It was at first, but I cleaned the rubber seal and ran some 0000 steel wool over the lip of the brass neck. It looks like these replacement parts and tools come from England, which will take a month. I wonder if it is possible to remove the NRV with a socket wrench? I may try that.
     
  5. snwcmpr

    snwcmpr SotM Winner Subscriber

    Offline
    Joined:
    Nov 16, 2011
    Messages:
    20,665
    Location:
    North Carolina
    Please read more about removing the NRV before you attempt it.
    Too many cautions than I can write.
     
  6. A A C

    A A C Norway SotM Winner Subscriber

    Offline
    Joined:
    Dec 2, 2020
    Messages:
    581
    Location:
    Norway
    @Ralph Vartabedian
    Hello . Before you do anything with the NRV , is the tank holding pressure ? A few pumps then open the pressure release screw see if it hisses. If it does then check your jet isn’t clogged . You may well have tried this but taking out the NRV without the correct tool can cause major problems . Otherwise follow the good advice from very knowledgeable members written above . Good luck :thumbup:
     
  7. ROBBO55

    ROBBO55 Subscriber

    Offline
    Joined:
    Oct 27, 2014
    Messages:
    2,310
    Location:
    Somersby, New South Wales, Australia
  8. Ralph Vartabedian United States

    Offline
    Joined:
    Oct 8, 2024
    Messages:
    3
    Location:
    USA
    I really appreciate the advice I have received here. I ordered a rebuild kit for the No. 51, which includes the NRV removal wrench, and it should arrive by the end of the month. It was advised that I attempt to pressurize the tank and then open up the filler cap or release screw to see if it releases pressure. It did not release any that I could detect. But when I first tried to ignite the stove, I could get enough pressure that the stove momentary ignited, but with liquid, not vaporized, kerosene burning at the orifice. I'm holding off on any other work until the rebuild kit gets here.