Coleman 508 loses pressure?

Discussion in 'Fettling Forum' started by JohnL, Sep 20, 2020.

  1. JohnL

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    Folks, recently picked up a good condition 508. Red knob on the on/off lever had melted at some point. Black control know was ok.
    20200917_210903.jpg 20200917_210850.jpg
    Before firing up first time, fixed some obvious faults. Pump cup replaced, fuel cap seal replaced, generator fuel on/off nut tightened a fraction, and also the flame adjuster nut. On firing it up first time, 25 pumps, then 60 after light, it worked pretty good. So I let it run a while then shut it down. When cooled down, put it back into its nice silver plastic case.

    Came back next day to find fuel had somehow leaked out from somewhere and had pooled at bottom of case. Tank/fount was practically empty after being 3/4 filled. Dismantled completely, this time taking out the fuel/air tube and inspected schrader valve. Noted it wasn't screwed in tight. Anyways, removed fully, lubed with a little silicone grease and re-inserted and tightened up firm. Did not touch generator as this was working fine.
    Re-lit and working. Shut off and after cool down returned to case. Came back next day, no leaked fuel, Yes! However, there was no pressure in the tank/fount. On re-pressurising, came back next day, only to find that all pressure gone. I have another 508 and a 533 and both hold pressure for a considerable amount of time.
    Any pointers to where this leak could be?
     
  2. Duck

    Duck United States Subscriber

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    Dunk test!
     
  3. Daryl

    Daryl United States Subscriber

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    +1 on dunk test. I always de-pressurize all my stoves soon after using and again before storing stops 99% of fuel spills. I know it does not answer your question but might fix your problem. Stay safe
     
  4. JohnL

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    Thanks Daryl, kinda makes sense to de-pressurise as you say.
    If I was to do a dunk test, what should I remove from stove, to make it easier to see any source of a leak?
    Cheers
     
  5. Daryl

    Daryl United States Subscriber

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    I would drain tank of fuel then pressurize tank and dunk without removing any parts. Keep it simple! May need to hold stove on its side so fuel pickup starts sucking air. I am thinking your 40 year old stoves on/off leaver does not turn off 100% . Turns off enough to put out the flame and when stove cools fuel becomes liquid. Might see bubbles from under burner exiting generator tube end. Since you don't have leaking fuel when running I don't think you will see bubbles anywhere else. When I store my stoves I make sure the on/off is off and leave the fuel cap maybe just snug so if pressure does build it can escape. Pressure can build in stored tank if you gain a few thousand feet altitude also. Some folks always drain fuel after use too. Other may have different advice on what to do which is always welcome. Stay safe