Burner problem

Discussion in 'Fettling Forum' started by EmmyLou, Aug 2, 2020.

  1. EmmyLou United Kingdom

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    Hi!
    I have recently purchased my first primus stove which turns out to be a number 4. 1939.
    I can get it to light and the flame burns well with a blue/yellow flame for a minute or so then puffs out to just a weak red flame. Can anyone help me with why this happens? Thank you. 20200728_175732.jpg 20200728_180729.jpg 20200728_181312.jpg
     
  2. igh371

    igh371 SotM Winner Subscriber

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    @EmmyLou - Welcome! Primus No.4 is a nice stove. You are right that the flame in your photos isn't what it should be. Looks like it has flipped into an 'underburn' - burning inside the top cap - the whole cap will melt if it isn't put out straight away when this happens, it can also do a lot of damage to the rest of the burner too. Looking through the red hot glow I think you have a wrong size outer top cap, and worse, one which is already in very poor condition. This is probably the cause of it not burning correctly.
    The No.4 stove actually takes an outer top cap that is smaller than the ones usually encountered. I can help source a correct one if that proves necessary, but it will be helpful if you could add a photo of what is inside that top cap when it is lifted off. That will enable us to see if there are any other parts missing or incorrect.
    Ian:thumbup:
     
  3. EmmyLou United Kingdom

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    Ian thank you. Really hoping I can get it burning well as its destined for my use daily in my polytunnel!
    . 20200802_102042.jpg 20200802_102049.jpg 15963601870011090916186025836287.jpg 20200802_102056.jpg
     
  4. igh371

    igh371 SotM Winner Subscriber

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    @EmmyLou - extra photos very useful - the outer is the wrong size and 'toast' as expected, but good news there doesn't seem to be any harm come to the rest of the burner. The inner sleeve looks OK, but just to be sure could you measure across the open base end - should be 36mm outside diameter (41mm is for a No.5 stove).
    Ian:thumbup:
     
  5. EmmyLou United Kingdom

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    It measures 41mm so that's wrong too.
    Could you advise me where to get a correct replacement from?
    You are being very helpful, thank you. Do the stoves have to run off any particular paraffin or can I steal some 28sec heating oil that my man uses for his vintage tractors? He thinks I'll get a dirty burn.
     
  6. igh371

    igh371 SotM Winner Subscriber

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    Heating oil should work, though it can smell a bit, otherwise 'premium paraffin' - but don't buy that at B&Q or a garden centre unless you've just won the lottery:lol: A trade supplier like RestExpress is a lot more economical and will give free delivery for an 8/10 gallon+ order.
    No.4 burner parts were still available until recently from Mike at Base-Camp in Peterborough (link), but I don't know if he has any left now.
     
  7. EmmyLou United Kingdom

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    A bit smelly :lol: no different to being surrounded by 1920/30's petrol/tvo tractors!
    I have sent base-camp an email so will see what he can come up with.
    Thank you for your help. I will let you know the outcome.
     
  8. Lennart F Sweden

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    Just checked fogas.se and they doesn't seem to have #4 size caps in stock now - at least not on website.
     
  9. EmmyLou United Kingdom

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    Thank you for looking for me.
     
  10. Brad Jackson United States

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    You might try BernieDog in the US. He is a great source of information ad may have parts.
     
  11. snwcmpr

    snwcmpr Subscriber

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    That would be BernieDawg.
     
  12. Brad Jackson United States

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    Yep, thanks for the correction. He is a great source of information.
     
  13. EmmyLou United Kingdom

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    Good news and bad news. I now have a new number 4 inner and outer cap courtesy of base camp. I have also got a new washer (filler cap?) and leather cup which haven't fitted yet.
    But I am still having the same problem. Could I be doing something wrong?
     
  14. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @EmmyLou Back to basics (apologies if you already know this)

    Underburn can soon melt and destroy an outer cap unless the stove is quickly extinguished.

    The way to avoid underburn is to never allow ignition of the flammable mixture under the outer cap.

    First, make sure the inner and outer burner caps are clean with no adherent rust or carbon flakes on their surface. If residues are on these surfaces they can glow once hot and cause early ignition of the air/fuel mixture. You should also check that the caps are properly seated on the burner so that no flame can slip under an edge.

    1. Pre-heat the burner using alcohol in the spirit cup, with absolutely no pressure in the tank.

    2. Allow the pre-heat flame to totally extinguish.

    3. Quickly close the air release, and pump the tank about 10 or so pump strokes.

    4. You should get clouds of white paraffin vapour/air mixture exit the many holes in the outer cap.

    5. Only now should you light this mixture with a match or flame applied above the outer cap.

    6. After 2-3 minutes of successful burn you can increase pressure gradually until full power is achieved.

    7. If, on lighting, the burner immediately reverts to underburn, release tank pressure and start the whole process again.

    Best Regards,
    Kerophile.
     
  15. Lennart F Sweden

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    If the burner jet is partially blocked or damaged, it could result in a spread stream of vapour under the burner that usually result in orange flames, soot ant nearly instant underburn - the vapour stream must be concentrated and centered in a silent burner.
    It is possible to check the jet function by having some fuel in the tank and pump a few slow strokes until you see the(hopefully) jet of fuel - then release pressure.
    This method should only be practised in a space where some fuel spill is no issue and in a convenient direction. "Don't pee into the wind"
     
  16. EmmyLou United Kingdom

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    @kerophile thank you. I did need to go back to basics as this is my first stove and I have had to watch numerous YouTube videos.
    This is the burn I've got now which seems pretty constant, but will occasionally splutter into and under burn but rights itself almost instantly.
    20200808_134151.jpg
     
  17. EmmyLou United Kingdom

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    @Lennart F I have checked the jet function and it squirts in a neat stream :oops:
     
  18. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @EmmyLou . I am glad that you have a good flame pattern.
    I am very fond of No.4 stoves and have several.
    Here are a couple with flame patterns to compare with yours:

    Primus No.4 - 1939 *

    Primus No.4 -1931.

    Most of the photos were taken in a workshop as a good blue flame pattern doesn’t show up very well in bright sunlight.

    Your flame pattern will stand a little more tank pressure in my opinion. You will soon see when to stop pumping when you start to “push” the flamelets off the burner cap.

    Please can you tell us the date code number on the base of your No.4 stove?

    Primus Dating Chart 1911 - 1964

    Best Regards,
    Kerophile.
     
    Last edited: Aug 8, 2020
  19. EmmyLou United Kingdom

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    Thank you everyone for your help. I have been having a play with how much pressure I need. I have also had my first coffee from it which made me silly happy.
    @kerophile its AD so 1939.
     
  20. kerophile

    kerophile United Kingdom SotM Winner Subscriber

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    Hi @EmmyLou . In the first picture you posted in this thread you show an “igniter” device clipped to one of the legs of your stove:


    Now that you have your stove operating well, it would be a good idea to take some additional photos of your lovely Primus No.4 stove, and post these in the Reference Gallery of CCS.

    Best Regards,
    Kerophile.