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Glow Plugs / Cold Weather

Discussion in 'A3/S3/Sportback (8P Chassis)' started by marklad2020, Jan 25, 2007.

  1. marklad2020
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    marklad2020 1st Gear

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    [Jan 25, 2007]
    Does anybody know if it is inadvisable to crank the engine before the glow-plug light has gone out? I notice that often in cold weather if I just turn the key all the way around and foget to watch / wait for the glow plug light to extinguish then the engine will still start cranking immediately even though the glow light is on. I would assume that if this would do any damage then the starter motor would be disabled until ready? Any ideas?

    Mark.
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  3. Rev-head
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    Rev-head Active Member

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    [Jan 25, 2007]
    Wont do any harm as i do this myself.......first thing in the morning i will wait but after that i just turnover
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  4. Amchlolor
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    Amchlolor Active Member

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    [Jan 25, 2007]
    I only wait first thing in the morning too.
    Rest of the time I don't bother.
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  5. icenutter
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    icenutter Member

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    [Jan 25, 2007]
    Doesn't do any harm - your engine might not start promptly if you don't - but I guess you could work that out yourself.
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  6. wilko
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    wilko Top Gear

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    [Jan 25, 2007]
    I thought that was the whole point of the light - wait til it's warm then start the car!
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  7. Amchlolor
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    Amchlolor Active Member

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    [Jan 25, 2007]
    I'm sure there are umpteen procedures we are 'supposed' to stick to.
    I know one of my wife's cars (can't remember which one) used to say you were supposed to wait for myriad of lights to go out before you turned the key.
    All sorts of 'system checks',like it's bloody Battlestar Galactica.
    Horlicks to that,just start the fecker.
    #6
  8. benw123
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    benw123 Moderator

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    [Jan 25, 2007]
    I usually also wait for it to disappear, but even in very cold weather it only seems to stay lit for a second or two.
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  9. steve184
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    steve184 Active Member

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    [Jan 25, 2007]
    the glow plugs are rapid at preheating so they are very fast at getting hot so literally by the time you switch them on they are hot enough to start the car. i always used to start the car as if it were a petrol and it always started on the immediately - only thing i noticed when really cold is it would start but it would stumble a little as it started but once it got going it was fine.

    I rememember when i had a 406 diesel and that just would not start unless you left the preheat light on and turned the key immediately it went out
    #8
  10. wilko
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    wilko Top Gear

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    [Jan 25, 2007]
    My 306 Turbo Diesel was the same!! Must be a Pug thing!
    #9
  11. Amchlolor
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    Amchlolor Active Member

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    [Jan 25, 2007]
    See what really bugs me about starting my car...
    When you turn the ignition on,the radio/cd will come on instantly.
    That's fine,no problem with that.
    However,when you turn the key further,to actually start the car,the radio goes off and takes a bloody age to come back on again.
    Maybe peculiar to Bose,I dunno.
    #10
  12. treblesykes
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    treblesykes Member

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    [Jan 25, 2007]
    same in a freelander radio doesnt come back on untill youve nearly got to where you are going
    #11
  13. marklad2020
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    marklad2020 1st Gear

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    [Jan 25, 2007]
    I also wait always for the light to go off, but usually the Missus doesn't remember to do that. The only thing that worries me is unspent fuel might damage the cat or particle filter if there is too much cranking as a result. Although I assume that if this was an issue then Audi would have disabled the starter motor until ready.

    Unlikely to be a big issue since here we havent seen much cold weather yet, but the forecast is for -10 during the next few days, so we will see.
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  14. Amchlolor
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    Amchlolor Active Member

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    [Jan 25, 2007]
    I'll sum up the difference between a company car and a bought-and-paid for car right here.

    My car,hardly bother waiting for the light.
    Wife's car,it's drummed into her head to WAIT FOR THE LIGHT TO GO OUT !

    :)
    #13
  15. rosscotdi
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    rosscotdi Member

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    [Jan 25, 2007]
    i was under the impression that the glowplug's came on when when you opened the door because it reakons you are going to start the engine??
    Any thoughts on this guys? it would explain the very quick heating eg 1 second!

    My works van is a astra and if you dont let the plugs do its thing it will turn over for 30-45secs before it starts
    #14
  16. SteveS
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    SteveS S6 avant

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    [Jan 25, 2007]
    my 1.9 tdi used to start straight away, never used to wait for the light.
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  17. OutLore
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    OutLore VOIP Dude

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    [Jan 25, 2007]
    I don't think Audi would stop the starter motor from turning until the light was out. Imagine how many duff calls they would get to the 24hr assistance line if they did...
    #16
  18. Caesium
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    Caesium My BM is fixed!

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    [Jan 25, 2007]
    The glow plugs heat up fairly quickly but its the compression of the air that ignites the fuel, the plugs don't get red hot instantly, and the light is not an indictation of when the plugs stop functioning, they stay on for about a minute, normally to burn off the crud.

    Not waiting for the light to go out, especially in high mileage cars can put excessive load on the battery due to the starter motor having to crank for longer. Its doubtful that any of this would damage the engine though.
    #17
  19. TDI-line
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    TDI-line Uber Post Whore

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    [Jan 26, 2007]
    Always wait for the light to go off, and if extremly cold will turn on/off a few times.
    #18
  20. steve184
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    steve184 Active Member

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    [Jan 26, 2007]
    well i never had any probs with mine just literally turning my key from off straight too 3 - just as if it were a petrol and it started immediately every single time - at the end of the day if it starts it starts - its not going to do any harm to anything by not letting the glow plug light go out.
    #19

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