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Intermittant cold start troubles

Discussion in 'Audi S4/A4/A4 Cab (B7 Chassis)' started by madstaff, Oct 29, 2012.

  1. madstaff
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    madstaff Member

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    [Oct 29, 2012]
    Wondering if anyone could shed any light on my rather annoying problem.

    I have a 2.0 TDI 170 avant which every so often takes a period of extended cranking to get it to fire up. It happens randomly, can be parked up for days and start first time, other times it refuses to fire up first time if left overnight.

    There are never any fault codes stored. Took a while to get going this morning, scanned for fault codes using a Snap-On SolusUltra - no codes.

    The fact no fault codes are ever recorded would point me to an actual 'mechanical' fault - maybe a fuel pressure problem via lift pump, tandem pump, injector seals??

    Anyone suffered a similar problem and have any pointers??

    Thanks in advance.
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  3. hades-
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    hades- Yorkshire & Humber Rep. Regional Rep VCDS Map User

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    [Oct 29, 2012]
    CTS
    batt on the way out
    glow plug or glow plugs
    #2
  4. madstaff
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    madstaff Member

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    [Oct 29, 2012]
    CTS - coolant temp sensor??
    If so, got one ready to fit along with 3 litres G13.

    Battery is good, tested fine with good CCA.
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  5. madstaff
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    madstaff Member

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    [Nov 8, 2012]
    Right, i've fitted a new battery, but i didn't think it was that anyway.

    I have however noticed in measuring block group 013 Injector deviation quantity that when cold (and theres a definite lumpiness/miss to the idle now and again) cylinder 1 is reading approx 2, whilst the remaining 3 injectors all read approx the same +/- 0.5 mg/s.

    As the car warms up cylinder 1 injector deviation quantity slowly starts to fall and more or less falls into the same approx values as the rest, and the idle smooths out.

    What could be causing this odd high reading when cold?? Any ideas?? What are deemed acceptable values for the deviation quantity??
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  6. Cupra neil
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    Cupra neil New Member

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    [Nov 13, 2012]
    I've just bought 1 of these and my mate told me to change the little 1 way valve on top of the fuel filter for the exact reasons you are describing, can't see them being that expensive so might be worth a go. He works for a vag specialist
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