Mixing tube trouble - Petromax 827

Discussion in 'Fettling Forum' started by HaakonJ, Sep 15, 2019.

  1. HaakonJ

    HaakonJ Subscriber

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    Hi

    I have a Petromax 827 where after about 20 minutes of running, the mixing tube is glowing red hot. The vaporizer is not nearly as hot (I could barely see a faint glow of red), so I suspect fuel is burning inside the tube. On my other 827, the mixing tube does not show any hints of glowing at all, no matter how long it runs. I can post pictures later. The lamp glows just as bright, and with the same calm hiss as my other 827. Nothing resembling the sound of underburn (like on a camp stove's silent burner). After I noticed this, I shut the lamp off and tried the following:

    - Checked and adjusted the air gap to about 12-13mm
    - Inspected the nozzle - did not seem worn by any means. All holes completely intact.
    - Tightened the nozzle and gas chamber (the part holding the nozzle)
    - Fitted a new mantle, burned it in.

    None of the above worked. The lamps were running at 2 bars pressure. Could this be caused by a bad jet? I didn't have a spare jet to try, but I could possibly swap one from another 827 that runs good, if this is a possible cause. What do you think? Any ideas that could lead me in the right direction? Appreciate any help I can get!


    Håkon
     
  2. JEFF JOHNSON

    JEFF JOHNSON United Kingdom Subscriber

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    It's worth a try.
     
  3. WimVe

    WimVe Subscriber

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    Hello Håkon,

    I would do the next things:
    - Switch fuelcap to eliminate any variation in pressure
    - check if the paddle if there is one is in neutral position, vertical.
    - check if the pointed screw which holds the J-tube has made a dent in this tube
    - check if he spray of fuel goes straight up
    - check if the ceramic nozzle is clear

    Btw any red glowing is not that a big problem. As long as your lantern doesn't backfire. This means strats to realy burn with loud noise inside the J-tube.
     
  4. HaakonJ

    HaakonJ Subscriber

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    Thanks, I will try your suggestions. Here is an image of the tube glowing. If it is not harmful to the lamp, I don't mind it. It works perfectly fine otherwise.

    IMG_20190911_084248.jpg
     
  5. WimVe

    WimVe Subscriber

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    You do have the right conination? 500 jet and 500 ceramic burner ?
    Looks like a lot off heat is coming back into the J-tube.
    I have seen it on meetings with extra warm weather and you get it when the pressure is to low but when you realy have burning fuel inside it you will hear it.
     
  6. MYN

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    Greetings @HaakonJ
    From the photo, I'd say the red heat is not just conducted or convected from the burning/glowing mantle.
    Its more probable that some of the fuel is burning inside the J-mixing tube. I have a Petromax 826 that behaves just like what you've just described for your 827...works near perfectly, just as bright, no growling sound,..just nothing except for the red glowing J-tube. Tried nearly every kind of adjustments for such lanterns but they do not seem to remedy that.
    Its not as damaging as some of the more spectacular back-burns we know of, but it'll still be damaging in the long run.

    I'd say its the J-tube. Replace or swap it if you have a spare.
     
  7. Matti Kucer

    Matti Kucer Sweden Subscriber

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    You had another 827 that was running good, so compared the J-tube, maybe it is bent?
     
  8. HaakonJ

    HaakonJ Subscriber

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    I just swapped the entire top part between the two 827's, and the «bad» top had the J-tube glowing again when installed in the other lamp. Took a while, and this time it dimmed down, suddenly, before the tube started glowing. There is definitely gas burning inside the tube. Not sure if the tube, nozzle or gas chamber is to blame. I have ordered a new J-tube and will start from there. Will clean the threads on the gas chamber and make sure it is a good fit when the new tube arrives.

    Håkon
     
  9. Juan

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    Try to swap the nozzle. Perhaps the holes are too big and doesn't work as flame arrester.
     
  10. HaakonJ

    HaakonJ Subscriber

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    @Juan
    Upon inspection the nozzle looks to be in good condition, but I can try that as well. Maybe it is not easy to judge by eye whether or not a nozzle is good? Thanks for the tip!
     
  11. Juan

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    Just try! If it doesn't work, so you can discard it as the problem and would be the U tube.
     
  12. WimVe

    WimVe Subscriber

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    I don't understand why you order a J-tube before you know what the real problem is. The tube is just that, a tube. any deformation would be visable.
    I think your pressure is not ok or the jet is getting blocked. If the flame can follow the fuel spary back most of the time the pressure isn't ok.
     
  13. george

    george United States Subscriber

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    I have an Optimus 930 that had that problem. The "J" tube would glow cherry red everytime I lit it up. I finally gave up and found a new "J" tube installed it and I've not had any problems since. That was about 8-10 years ago. My 930 still runs hot but no glowing "J" tube. This seems to be a characteristic with this model.
     
  14. HaakonJ

    HaakonJ Subscriber

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    @WimVe
    Not sure you read/understood my post #8 completely? Sorry about any bad phrasing on my part! I believe I have narrowed it down to either the J-tube or the nozzle. The nozzle looks to be in very good condition. I didn't mention this in the previous post, but the J-tube is heavily dented from the set screw, and the paddle screw is very loose and looks bad (misshapen).

    @george
    Good to hear! Hopefully it will solve my problem as well.
     
  15. WimVe

    WimVe Subscriber

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    Ah yes then a new one would be a good idea.
     
  16. george

    george United States Subscriber

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    For sure!!! :D/:thumbup:
     

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