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Q7 3.0 TDI Starting Problem

Discussion in 'Diesel forum' started by zed, Apr 1, 2011.

  1. zed
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    zed New Member

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    [Apr 1, 2011]
    My Q7 has a problem. From cold, it takes a good 4 or 5 seconds of cranking to start, and then it kind of coughs once and starts up.

    If I then drive it a mile or two and switch off before it has achieved full operating temperature, it will re-start cleanly, but will still crank for 4 seconds or so.

    However, if I drive it until it's at full operating temperature, and stop for fuel or a short stop at a shop and try to start it, it will crank forever without starting. I can get it started every time, but it takes 4 or 5 attempts of cranking for 7 or 8 seconds at a time, then it will fire cleanly.

    This issue is consistent in that I can make the problem occur by driving until full temperature is reached, then park up for two minutes, and when I try to start the engine again I have to crank it over 4 or 5 times for 7 or 8 seconds each time before it fires and starts up cleanly.

    The issue will only happen once per day, so any subsequent starts the same day after the above issue will start first time, but still takes around 4 seconds of cranking.

    Otherwise, the car runs fine once it's started.

    The fuel filter has been changed, and it's a new battery too.

    I have VCDS and no errors are reported.

    Any ideas?

    Thanks!
    Last edited: Apr 1, 2011
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  3. Gavin0478
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    Gavin0478 Active Member

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    [Apr 15, 2011]
    as a silly answer id say possibly a temp sensor is not working correctly so doesnt know whether to use glow plugs and hot/cold start maps.
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