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Tdi Starting problems

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by s1hal, May 21, 2008.

  1. s1hal
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    s1hal New Member

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    [May 21, 2008]
    If not used for a few days my 1.9tdi has a problem while starting. It turns over ok so i dont think its battery related. Once it starts it splutters a bit and i get a cloud of black smoke like its chucked too much fuel through. After a quick rev it runs fine again. I thought I saw a post here a few months ago about the pd system not returning fuel properly but can't find it now. Was just wondering if anyone has had the same problem or had an idea as to what could be causing it. Thanks in advance ;)
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  3. technics100
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    technics100 Member

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    [May 21, 2008]
    mine does exactly the same. It always has, its far worse when its cold. My car is in for a service in a few weeks, I will ask the mechanic when its in. Possible fuel filter? How many miles is on ur car?
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  4. s1hal
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    s1hal New Member

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    [May 22, 2008]
    its only just hit 30k mls. I bought it at 25k and its done it since i got it. The problem was a lot worse on cold mornings too. be interested to find out how it is after your service.
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  5. evilscotsman
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    evilscotsman Space Cowboy

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    [May 22, 2008]
    The first point of call on a diesel thats hard to start and spluttery from cold, is the heater plugs / glowplugs.

    If the air in the cylinders is colder than it should be the engine will not start, the cranking for longer gradually heats the air charge by pump action and the engine starts but runs roughly until its reached a minimum operating temp in the cylinders. Working glowplugs super-heat the air in the cylinders directly while the orange light is on, to make the engine start quickly and easily.

    Try putting the ignition on for a few seconds then off a few times to get maximum heating effect from the existing plugs (when cold) and see if it starts easier, the repeated ignition use builds the heat in the plugs when they arent too good and improves starting in most cases, unless more than one glowplug is completely dead. (broken link cable between them? can happen)

    They are cheap usually and fairly easy to replace.

    (The other reason can be low fuel pressure to the injectors at cranking speeds, which are typically about 300 to 400 rpm, and when it starts the revs lift to 1200 ish, producing more average fuel pressure and improving combustion, as vacuum is weak when cranking compared to idling once started, and a vacuum pump drives the fuel pressure regulator on a common rail diesel engine, and diesels don't have vacuum in the inlet chamber at all unlike a petrol engine, so the pump runs slower during cranking.)

    Check for fuel leaks from injectors and pipework, faulty vacuum pipes to the FPR, faulty FPR, or poor / faulty glowplugs.

    :)
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  6. s1hal
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    s1hal New Member

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    [May 27, 2008]
    Left it from Saturday until this morning without starting it which is long enough for the problem to occur. Tried what you suggested about turning ignition on and off a few times and it started perfectly so hopefully it is just a glow plug issue.

    Many thanks Evilscotsman
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  7. evilscotsman
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    evilscotsman Space Cowboy

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    [May 30, 2008]
    ah, no problem my son! Glad to hear that worked, so I would now get a set of GP's from vagparts and shove them in, clean and tighten all connections including your battery lugs and any earth cables and you should be good for years :O)
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