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Thread: Just How Glow Can A Glow Plug Glow

  1. #1
    Join Date
    Jul 2006
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    lyndoch south australia
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    Just How Glow Can A Glow Plug Glow

    My Landcruiser Is Fitted With An Automatic Timer To Acuate The Glow Plugs. I Have Fited An Overide Button To Extende The Cycle Which Aids Starting On Cold Mornings Heaps. Qu. Is There A Critical Time Limit As To How Long Current Can Be Supplied To The Plugs Without Them Burning Out Or Should It Be Possible To Have A Plug Glowing Away Happily Without Self Destructing.

  2. #2
    Join Date
    Sep 2006
    Location
    Adelaide
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    Re: Just How Glow Can A Glow Plug Glow

    Your battery will go flat before you burn the heaters out.
    Glo plugs consume about 10Amps each (give our take a bit depending on size). 6 of them turned on at once=60A. Most batteries (even in good condition) will die in the arse after a few minutes of having that much current sucked out of them. As the voltage of the battery goes down, the current required for the glo plug goes up, which sucks the battery voltage down even further and well its a repetitive cycle.
    Glo plugs are a straight out resistive device designed to radiate heat, it is very difficult (not impossible though) to destroy such a device in the circumstances you describe.
    David is correct with the assertion that you get no more effectiveness from them once they are hot.
    Rgds

    Adam

    "Revolution never comes with a warning!"

  3. #3
    Join Date
    Sep 2006
    Location
    Adelaide
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    193

    Re: Just How Glow Can A Glow Plug Glow

    Something else I just though of, which further supports my theory that you will have some difficulty killing them and more directly answers your q.
    A lot of places that sell conversion kits sell inline heaters that utilise a glo plug to supply the heat. These are normally temperature regulated but this is done so as not to burn the oil passing through the device, not to stop the device destroying itself.

    David, I just read your post again, do you by any chance have a teenage daughter, if so it LIKE shows!!
    Rgds

    Adam

    "Revolution never comes with a warning!"

  4. #4
    Join Date
    Sep 2006
    Location
    Belgrave - Melbourne
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    54

    Re: Just How Glow Can A Glow Plug Glow

    Hi Folks, I manufacture an inline heater using a glow plug as the heating element. I am advised by NGK that the glow plugs are designed to be on briefly say 6 seconds. Keeping the glow plug on for much longer than this will burn it out quickly. In the heating units, the glow plug doesn't burn out because it disperses it's heat into the fuel. It is common for my customers to burn out the glow plug on installation because they just can't wait to see if it works before it has been primed with fuel.

    Regards
    Marcus

  5. #5
    Join Date
    Jul 2006
    Location
    lyndoch south australia
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    332

    Re: Just How Glow Can A Glow Plug Glow

    thanks all for response
    vegiecars, that was my worry as my timer [before it died] would stay on for about 3 to 4 seconds and
    i thought if something generates enough heat to glow red hot in 4 sec that heat would very soon self destruct
    i know they remain on constantly in fuel heaters but the cooling effect of a cool liquid is very diferent to sitting in still air
    i will tred lightly and with trial and error use the lowest count for a clean start
    it seems to be about 7 to 8 sec

  6. #6
    Join Date
    Sep 2005
    Location
    WA
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    4,205

    Re: Just How Glow Can A Glow Plug Glow

    On my '78 300D engine, it takes 10 seconds for the GP to be hot enought for reliable winter starts on biodiesel/veggie blend. These are the series GPs MB used before 1980.

    Tony

  7. #7
    Join Date
    May 2006
    Location
    Maitland, NSW Australia
    Posts
    180

    Re: Just How Glow Can A Glow Plug Glow

    In my 300D, I have a home-made glow plug heater which uses a single 14V pencil-type glow plug. My GP heater which sits before the IP is controlled by a 100degC thermo switch, so it is constantly cycling on and off. In actual fact, I thought it was a 24V volt GP as that is what I asked for, but have since noticed that 14V is etched onto it????!!! Previously I was blowing the 12V variety quite regularly (11V etched on that GP). Anyway, this single 24V/14V (whatever) plug has worked flawlessly for the past 10 months and does an excellent job at heating the oil.

    I think the secret is to use a nice lump of brass for these GP heaters. They heat the oil that passes though instantly, but as soon as the fitting gets to your selected temperature, the housing does most of the heating and the GP doesn't have to work as hard, so cycles off and on less often. Also, it retains a lot of it's heat if you have stopped for 1/2 hour or so. It will do an even better job if you take the time to insulate it.

    BTW, I am getting this reliability from a $10 GP off eBay! A word of warning though. Strip the paint off it before installing it or you run the risk of the paint entering your fuel line.
    Cheers
    Bruce
    http://oztayls.blogspot.com/

    1976 W123 300D (3 litre 5-cyl NA diesel running on SVO since June 2006)
    1982 W126 280SE (Sadly is For Sale)
    1993 W124 300D (3 litre 6-cyl NA diesel - being converted to SVO)

  8. #8
    Join Date
    Apr 2007
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    Bungendore
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    12

    Re: Just How Glow Can A Glow Plug Glow

    Quote Originally Posted by David View Post
    To the best of my knowledge, glow plugs keep glowing when the engine is running with no power applied from the heat of the combustion in the cylinder. I think running the heating element which is inside the plug is a different thing however and overly long heating times can shorten their life.
    Once the engine is running the glow plugs are inoperative and serve absolutely no function. At my work we have some diesel machines that dont have glow plugs (dont ask me why? cutting costs and lowering complexity probably), they are quite hard to start but run fine once their going

  9. #9
    Join Date
    Sep 2005
    Location
    WA
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    Re: Just How Glow Can A Glow Plug Glow

    TImo306,
    Glow Plugs for a diesel engine are norrmally installed in Indirect Injection engines to provide additional heat for engine starting (the prechamber causes a significant loss of heat in the air, during the compression stroke).

    Direct Injection diesel engines rarely have GPS fitted. This may be the difference between the diesels at your work.

    David was not implying that the GPs were powered up, just that he thought that they would continue to glow due to the heat of combustion in the prechamber, where the GPs are located, once the engine was running.

    I doubt that they would continue to be red hot but neither of us has any evidence to support these opinions or else we would have presented it.

    Regards,
    Tony
    ps, check for a Privarte Message from me.

  10. #10
    Join Date
    Apr 2007
    Location
    Bungendore
    Posts
    12

    Re: Just How Glow Can A Glow Plug Glow

    Quote Originally Posted by Tony From West Oz View Post
    TImo306,

    David was not implying that the GPs were powered up, just that he thought that they would continue to glow due to the heat of combustion in the prechamber, where the GPs are located, once the engine was running.
    My bad, I misread his post.
    In regards to direct injection diesels, dont the new VW diesels etc have glow plugs? Ive never driven one so i cant say but I thought they did.

    That would logically explain why the engines at my work dont have glow plugs

    Tim

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