Mk2 Golf 16v cold start problem

Discussion in '16-valve' started by mbradbrook, Mar 23, 2008.

  1. dan_1987

    dan_1987 Forum Member

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    http://www.auto-solve.com/mech_inj.htm#MFI05

    Accumulator:
    "Its first job is to help smooth out any pulses in the flow of the fuel, this is achieved by passing the fuel through a series of baffles and into a chamber giving it slight capacitance and a much smother flow. Its other and possibly more important role is to maintain pressure within the system when the fuel pump has been switched off; this is achieved by the accumulator spring and diaphragm pushing against the fuel.
    For the duration that the engine is running, the diaphragm will be against its stop within the spring's chamber. When the engine is stopped and all of the non-return valves close, the spring pressure against the diaphragm will maintain the residual or holding pressure and overcome any slight seepage.

    Within the data books for this system, it is shown that the critical time for maintaining these pressures, is between 5 and 20 minutes. After a journey, when the engine is switched off, the under bonnet temperature increases causing the fuel in the lines to heat and it attempts to evaporate.
    Maintaining the pressure eliminates this problem and ensures a clean start when the vehicle has been standing with a hot engine."

    Sorry, can you clarify your last statement:

     
    Last edited: Mar 30, 2008
  2. dan_1987

    dan_1987 Forum Member

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    Are we still talking about a cold start problem? My car will fire up easily after 4-5hours if the engine was warm. I don't class this as a cold start tbh. My 16v seems to struggle if its stone cold (left over night) but it fires quickly enough and only runs a bit rough for 5-10 seconds.
     
  3. mbradbrook Forum Member

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    Just an update to this thread. I checked the timing on the car and had to retard the dizzy about 5mm to get the markers to line up. The car now starts on the button whether hot or cold. What i have noticed is that when it is warm the idle hunts by +/- 100rpm continuously. It has got a brand new ISV on it so i don't think it is that. Do you think the mixture needs adjusting? Is the only way to do this at a garage with a CO meter?

    Thanks for all your help:)

    Matt
     
  4. judderi Forum Member

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    You could buy your own co meter. Always handy to have.
     
  5. 2dubnick Forum Junkie

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    My car has identical problems as yours did, I have replaced/checked everything. I will go try the timing in a minute...fingers crossed this is driving me nuts!
     
  6. richarddane Forum Member

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    mine as a very similar problem, mine is mk2 2.0 abf 16v

    the car struggles to fire up on its own, but as soon as you dab the accelerator it fires up, it idles a little rough so i keep my foot on the accelerator at about 1500rpm for a bout 30 seconds and then it seems fine. it runs fine, accelerates fine etc. any ideas?
     
  7. judderi Forum Member

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    Depends what injection system your ABF is running. If its K-jet then check timing and id also advise cleaning up the flap in the metering head and making sure it is not sticking. Also there is a spring inside which holds the flap up a little for starting which sometimes falls to one side and just needs pushing back over. If its the electronic injection your best bet is to change the temperature sensor, not 100% which one though.
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    symptoms of bad co adjustment or a faulty WUR. I'd start by just giving it a complete once over, check all earths, check all rubber pipes/boots for splits, check all vacuum lines, check ignition timing etc. If everything looks ok then I'd look at the WUR, try disconnecting the plug on the side of it, if it helps that suggests mixture is too lean or cold control pressure is too low.
    Get mixture set to 2% by a garage and idle reset if changed, see where that gets you.
     
  9. richarddane Forum Member

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    Thanks Judderi.

    I thought i had both the k-jet and electronic ignition, is this not possible?

    To check the flap and spring do I take the air intake pipe off, is it inside near the idle adjustment screw?

    Thanks Rubjonny, I've done 2 checks on the WUR as described in the haynes manual. One is to see check the resistance which should be between 20 and 26 ohms, mine is 24. The other is voltage, which should be a minimum of 11.5 volts and mine is 10.5. Does this mean this is faulty, or is something else causing the 1 volt drop?

    Help much apprecaited.
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    judderi was refering to the mk3 abf managment by 'electronic', you have fully electronic ignition + k-jet on a KR :)
    you pop the air boot off and check the position of the round flap, it should be flush with the narrowest point on the side closest to the front of the car.

    as for wur checks this tells you the heater inside is ok and it is getting voltage, but not if it is controlling the warm up pressure properly unfortunatly :(
    voltage does seem a little low, whats the battery voltage like? mine was giving similar issues which cleared up after i unplugged the wur, suggesting its not working or theres summat up with the mixture adjustment. it runs ok as it is so im going to leave it alone, since im ripping it all out for abf stuff once the cab is on the road in a few weeks :)
     
  11. richarddane Forum Member

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    Thanks Rubjonny. Is this on top of the air box or near the idle adjustment end? Thanks
     
  12. rubjonny

    rubjonny Administrator Staff Member Admin

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    airbox end :)
     
  13. richarddane Forum Member

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    thanks, so can you unplug the connector on the wur and the car will still start? if so, if i unplug it and it starts up fine does this tell you theres a problem with it?
     
  14. rubjonny

    rubjonny Administrator Staff Member Admin

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    yeah the wur plug just makes the car come 'off choke' quicker, on mine it fixed the issue either becasue the wur was leaning off the mixture too much, the wur cold pressure is wrong or there is a problem with co adjutment. cant be assed to look into it in any detail as its coming out soon
     
  15. richarddane Forum Member

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    thanks rubjonny, ill try it and let you know the result.
     
  16. richarddane Forum Member

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    here's the results rubjonny. I unplugged it and it seemed to start up ok (but it does start up ok sometimes anyway) and idle at about 1200rpm. You could rev it up and it wouldn't stall. Then after about a minute the revs dropped to about 950rpm, and when you revved it up and took your foot off, it would stall, and then struggle to start without help from the accelerator pedal. It i fine after about 2 minutes when it has warmed up a bit. What does that rule out if it didn't make a difference, what can I try next? Thanks
     
  17. pigbladder Forum Addict

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    get some gauges on the fuel system

    the wur should be the same when cold if its plugged in or not , the wire just makes it warm faster and come off choke /cold start
     

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