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weird problem NOT FIRE-ING

Discussion in 'Diesel forum' started by vw754, Mar 15, 2007.

  1. vw754
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    vw754 vorsprung Durch Technik

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    [Mar 15, 2007]
    ok,car takes 3-4 second to start,hot or cold it dont make any difference.

    it will start (eventualy 4 seconds after turning the key) but at first it will not ,it just wont fire, to give you a better idea,as if there is no fuel:think:
    new filter plus the T-piece that fits on top of fuel filter and new seals,and no faultcodes via vag-com.

    What should i do now!!!:keule:

    also some smelly fumes can be smelt when standing with car running.

    A4 TDI (B6) AWX ENGINE....NO VISIBLE LEAKS OR SPLIT HOSES........THAT I CAN SEE!
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  3. Rev-head
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    Rev-head Active Member

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    [Mar 15, 2007]
    Glow plug problem maybe?....try and heat them 2 or 3 times before you try and start the car and see if that helps....if that does help your problem lies there i think
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  4. Rev-head
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    Rev-head Active Member

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    [Mar 15, 2007]
    What mileage is on the car
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  5. golisago
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    golisago Member

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    [Apr 1, 2007]
    I would tend to agree with the above....and ask you if you have had a timing belt change recently..which if so in many cases retards the timing a little caursing this proble plu owners reporting there cars seaming to be some what slower afterwards.
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  6. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 1, 2007]
    Cant be timing,car starts perfect for 3-4 days then problem returns.
    as for the glow plugs, hot car turn it off,immediatly re-start...same problem and also when it was very cold/snowy weather,it started 1st time in the morning! (must av been in a good mood...again!) mileage is 100k+.
    Timing belt was changed 8 months ago,problem started 4 months ago. changed fuel filter,t-piece on top of filter,coolant sensor,cleaned egr,checked intank pump see if all pipes are ok(in tank pump and seal replaced 9 months ago with a new seal from audi. Also new genuine audi maf sensor fitted. BAD m.p.g 91.9 pence per litre 16.00 pounds of diesel (17.41 litres) 98 miles was all i got local town driving,should i get better?
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  7. inigoj
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    inigoj Member

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    [Apr 1, 2007]
    If you have had a recent timing belt change and you are getting a low mpg and slow starting problems it could be that your timing needs re-adjusting or injectors/pump re-calibrating.

    Otherwise if your battery and starter are all ok, it could be air in the fuel system. Is your new 'T' piece sealed/seated properly? Is the water drain bolt tight.

    Or glow plugs, worn injectors?

    It is strange that it is intermittent, if you have vag-com check your idling fueling, and reported air volume.
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  8. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 1, 2007]
    injector readings ok,sebastian checked out the readings,coolant sensor temp is 86.6 on vag-com,all seems ok.
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  9. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 1, 2007]
    882 revs on idle maf ok,how can i see if its fueling more than it should,also dont smoke black from exhaust.

    If glow plugs worn how can i check + would it not do this all the time if glowplugs were worn,sometimes car starts 1st time when been standing for 15 hours+
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  10. golisago
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    golisago Member

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    [Apr 1, 2007]
    When you say the timing looks ok is it smack bang in the middle of the graph!
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  11. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 1, 2007]
    well,not checked really but,if it was out,even slightly,the problem would be there all the time,not there 3-4 days then maybe next 2 days be mint at starting!

    Also now when i floor it it holds back for a second then throws a puff of black smoke out then go's (like a flat spot) but,only does it now and again!!
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  12. inigoj
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    inigoj Member

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    [Apr 1, 2007]
    If the problem comes and goes it could be a dodgy glow plug relay.

    Most TDI's will hesitate when accelerating at very low revs and give a puff of unburnt fuel smoke which vanishes as boost comes on line. If it does this above 1700rpm you may have a slight leak on boost/control side or worn sticking boost N75 valve/timing/fueling.
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  13. golisago
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    golisago Member

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    [Apr 1, 2007]
    Yes inigoj he should check all of those and as well as the n75 i would use some else's maf sensor if you know someone who has the same.........because the hesitation does fit a bad maf scenario.
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  14. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    ok,if its the glowplug relay,where is it located and what colour is it(for identification)

    Also this problem persists even if i turn engine off and then back on(re-start) instantly. does the car need glow plugs to be working even when cars hot?

    What exactly does the N75 valve do,and where is it located on my engine (AWX ENGINE) if faulty would it give bad fuel economy and would it show up via vag-com? no fault codes are found via vag-com at present.

    New maf sensor fitted 2 weeks ago (dealer part)

    N75 valve/timing/fueling ?????????????? explain.

    car currently only doing 100 miles on 16.00 pounds of diesel (17.41 litres @91.9 pence) i think its thirsty,or is this how 130 bhp are (driven steady)
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  15. Caesium
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    Caesium My BM is fixed!

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    [Apr 2, 2007]
    The pump timing cannot go out by changing the belt as its common rail! only the cam timing can go out, and if its out then it'll run rough all the time, not just some of it. It's something else, maybe fuel filter (i have heard of a piece of **** in the system causing problems)
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  16. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    fuel filter changed twice in 4 weeks! cars been like this for a few months now.

    I always keep a full tank aswell
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  17. golisago
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    golisago Member

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    [Apr 2, 2007]
    I believe that like my X5 common rail setup the rail has an inline filter/valve at one end of the rail......do you know if this has been changed!!
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  18. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    non return valve changed.

    My injector readings (2 months ago) -0.75 /-0.42 /0.66 /0.52 mg/str
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  19. golisago
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    golisago Member

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    [Apr 2, 2007]
    What is the reading now! another thing you can try is just b4 you turn the engine of have the wife/friend clamp the top hose of two wich are located at the bulk head at cam cover level.........it should have a blue mark on it.

    Then shut her off , in the morning when your re-starting the car have someone take the clamp off and if it starts this means that the injection system is loosing pressure from a seal on the left hand side or the pump at the back of the engine.

    Can i also ask if the car is/has been re-mapped at all or has a tuning box in place.
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  20. inigoj
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    inigoj Member

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    [Apr 2, 2007]
    It seems that your problem could be sensor or software related.

    If your car will not start straight away when you cycle the ignition and the engine is hot, it cant be a fuel/air leak.

    As its a PD the only thing that could trouble the timing is the crank/engine position sensor, but if the car runs fine it is not this.

    From what you have said it sounds like your car starts a little better when it is stone cold. This suggests that something different is happening when the car is hot. The later engines do not always use 'cold start' as the earlier TDI's did.

    There seem to be a lot of TDI owners who are having the same slow start problem, but there does not seem to be a single cause or difinitive solution.

    I would check the operation of the coolant and fuel temp sensors, and not to ignore the obvious, check and maybe lubricate the starter motor, and clean & check all the relevant contacts and earth straps and battery. If the starter is not turning the engine fast enough, your ECU will not fuel the car.

    If your car has very high mileage you could be loosing compression, or if your car has been chipped it could be affecting the hot start.

    My best guess is that your problem is not mechanical.
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  21. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    can you explain software related?
    car has no tuning box and is not remapped.
    The only think i took off was the egr,gave it a good clean and put it back.
    Still,its got plenty of power!
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  22. inigoj
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    inigoj Member

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    [Apr 2, 2007]
    By 'software' i mean some people seem to be of the opinion that as the ECU adapts to the running conditions of the car, and as various electrical connections/sensors slightly degrade over time, the car is adjusting something that is causing the 'unexpected feature' of slow starting.

    If you have your radio code etc, you could try disconnecting your battery for 10 mins, this should reset your ecu to default settings.

    If your car then starts immediately it means that the problem has been caused by ECU adaptation or sensor problems.
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  23. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    thanks for that info. i had vag-com connected to the car yesterday,so any resetting is clear.

    Cars booked in at diesel specialist on thursday,told them its been on vag-com and no faults found. Maybe they got the know how what and where knowledge/equipment.
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  24. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
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  25. golisago
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    golisago Member

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    [Apr 2, 2007]
    Good look....they should sort you out!!
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  26. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 2, 2007]
    Hope they can, Guess what? although mpg and starting probs may not have been cured,its been driving mint today! i wonder why?....uuuummmmm:wtf:
    #25
  27. golisago
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    golisago Member

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    [Apr 2, 2007]
    Cos you cleared the codes......try deconnecting the battery for 20mins and then re-connect it and take it for a ride.
    #26
  28. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 4, 2007]
    [​IMG] Yesterday, 11:05 AM #12 pbb vbmenu_register("postmenu_1675448", true);
    Newbie

    Join Date: Apr 2007
    Location: Portugal


    [​IMG] I couldn't believe!
    My friend,
    try starting the car with the headlights on!

    If it starts ok, like I think it will, you'll have to change the headlights switch. Around 70€ plus taxes!

    I only found out the problem, checking the fuses in the garage, abd starting the car with the lights on, thing that I never do!

    Good luck, and pass the word, there is a lot of guys with the same problem!
    #27
  29. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 4, 2007]
    Well i did what the above person has said and my car starts perfect!!! 100% perfect....but why?,what has the switch got do with starting?.....anyone???????
    #28
  30. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 5, 2007]
    any ideas on where a fuel radiator is on the a4 tdi b6?
    #29
  31. golisago
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    golisago Member

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    [Apr 5, 2007]
    Do you mean the fuel cooler!!
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  32. vw754
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    vw754 vorsprung Durch Technik

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    [Apr 5, 2007]
    yes! oh and do you have to ever replace the cooler for any reason? do they stop working or etc,etc?
    #31
  33. Caesium
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    Caesium My BM is fixed!

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    [Apr 5, 2007]
    fuel cooler? never heard of it!
    #32
  34. golisago
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    golisago Member

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    [Apr 6, 2007]
    #33

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