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2.0 TDI Glow Plug Testing

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by ricochet, Apr 29, 2013.

  1. ricochet
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    ricochet Member

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    [Apr 29, 2013]
    Hi,

    Does anyone know how to properly test the glow plugs in a 2.0 TDI engine?

    Don't know what voltage to expect, but was told that a straight 12v across the glow plugs would ruin them. Its a BRD engine by the way, so has ceramic glow plugs.

    Also not sure if the coolant temp' sensor affects whether they 'glow' or if thats controlled by something else.

    All help VERY welcome!

    Cheers
    #1
  2. ricochet
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    ricochet Member

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    [Apr 30, 2013]
    SANY0229.jpg SANY0228.jpg
    OK, had a go at live testing the plugs this morning...

    Removed valve cover and unplugged glow plugs. Cleaned oil out of the electrical plugs and also found two of the wires had nicks in the insulation, so sealed these with self amalgamating tape - see photo of nick in wire.

    Checked resistance of each glow plug between the hex' and the tip which connects to the plug - all reading 0.9 - 1.3 ohms. NOTE: Had to press hard with the meter probes, as the initial reading was about 35 ohms.

    Plugged all the glow plugs in and laid an 18" extension bar across the valve rocker to create an earth. Rested the hex' of the glow plugs on the extension bar to earth the glow plugs, then turned the ignition on - none of the plugs glowed.

    Cleaned out the electrical plugs which connect to the glow plug tips, then checked the voltage at each electrical plug when the ignition was turned on. Initial voltage is 12v for approx' 1 - 2 seconds, dropping down to 7v for another second, then down to between 5 & 5.5v constant. All electrical plugs read the same.

    Then tried connecting the glow plugs again, earthed through the extension bar touching the engine, and they worked OK - see pic of two of them glowing. Careful if you do this not to grab the end of the glow plug when unplugging them again - it's just been up to around 1600degC.

    Put everything back together and it started fairly slowly - probably due to me messing on with the glow plug testing over and over again and draining the battery a touch. Will feedback how it starts on the next cold morning.

    Not convinced the electrical plugs give the tightest connection onto the glow plugs themselves, but we'll see how we get on.
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  3. evildream
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    evildream New Member

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    [Feb 16, 2015]
    Hello there,

    I also have a 2.0 TDI and i'm trying to diagnose my slow cold start in the morning. Battery seems to be ok. I noticed that when i turn the key 3 or 4 times and the try to start, it seems better... is this an indication of glow plug problem or something else?
    Thanks.
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  4. desertstorm
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    desertstorm Well-Known Member

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    [Feb 16, 2015]
    The glow plug nominal voltage is around 4.4V not like traditional glow plugs which are 12V . There is an electronic controller that applies 12V initially and then drops this down by electronically.
    This results in very fast warm up of the plugs but if you connect them to a 12V supply they will burn out in seconds.
    Glow plugs do lose there efficiency over a period of time and won't heat up as much as when new.
    The glow plugs only activate when the engine temp is below around 9-10 degrees.So if you have an issue with the coolant temp sensor then they may not even be turned on.
    How old is the car battery, they don't last forever.
    Karl.
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  5. evildream
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    evildream New Member

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    [Feb 16, 2015]
    Just curious: about losing efficiency, do you know if these glowplugs are different from the old ones on 1.9 TDI engines? I had a 1.9 TDI pd 150 from 2002 and NEVER had a starting problem... 2.0 tdi seem to have a lot...

    Anyway, my battery is 10 months old (from previous owner) and it's 74Ah 600A, don't know if specs are affecting the cold start...
    I've measured the battery and reads 12.3v and drops to 10v when starting, which i believe is ok.
    I'm tempted to upgrade the battery to a better one with higher amps but i'm skeptic about it...

    Thanks.
    #5

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