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Cold Start issues

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by North East Car Care, Dec 5, 2012.

  1. North East Car Care

    North East Car Care New Member

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    Joined:
    Dec 5, 2012
    Location:
    Hartlepool
    Your Mercedes:
    G reg 300E
    Sorry for his being my first post lol

    I`ve just bought a G reg 300E automatic and seem to be having some cold start issues, the car seems to be turning over but not firing at first then firing on a couple cylinders before slowing firing on all cylinders but feels sluggish to tick over

    Any advice on what to look at first please :confused:
     
  2. CRH71

    CRH71 Senior Member

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    Joined:
    Jun 11, 2012
    Location:
    Kent
    Your Mercedes:
    C250 TD
    Sounds like my old 280E when the "Fuel Pump Relay" (which actually contained some sort of electronics to control the mixture during cold start) started going faulty. Watch it - this part is one arm, one leg and several other body parts from the Dealer if you need one, and it MUST be the correct part number for the vehicle - don't take it as gospel that the one on your car is correct - they're easy to swap with a scrapyard one and it may be a different part number so won't work properly on your car.

    It could also be the "Warm Up Regulator" not functioning (again, VERY expensive - buy it directly from Bosch as this will save a fair pile of cash - better still, get friendly with a Bosch employee and ask them to get it for you) or the supplementary cold start injector not firing. It could even be as simple as a blocked fuel filter, or cr@ppy injectors.

    Cheap options first - try a new fuel filter and see if that improves things.

    Check cold fuel pressure, check the warm up regulator and check that the FPR is the correct one - when I put a 'scrap' one into mine (different part number) the car became a class A PITA to start from cold but was perfect when warm!

    Failing that, find yourself a good rolling road operator that understands the K-Jetronic system (I know of one in Kent, but that's a mile or two away from you!) and get them to check it over - for the sake of an hour or so's labour on the rolling road, they'll be able to definitively confirm the fault and save you swapping some (bl**dy expensive these days) parts about for no reason or gain.

    HTH
     
  3. CRH71

    CRH71 Senior Member

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    Joined:
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    Location:
    Kent
    Your Mercedes:
    C250 TD
    Last edited: Dec 6, 2012
  4. robparker

    robparker Senior Member Authorised Forum Supporter

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    Location:
    Taunton
    Your Mercedes:
    C55 (203), 220d (115), 200d (110)
    The 300 engine has a different setup to the old 280, so it doesnt have a warm-up reg like yours does.
    Assuming you have tried cleaning out the dizzy cap, then I would try an OVP relay to begin with, you wont necessarely get an ABS light on to say its faulty, but it will make cold starts hard.
     
  5. OP
    North East Car Care

    North East Car Care New Member

    Messages:
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    Joined:
    Dec 5, 2012
    Location:
    Hartlepool
    Your Mercedes:
    G reg 300E
    Thanks for the replys guys, so far ive replaed the plugs and leads and the fuel filter is getting replaced today.

    Whats the OVP relay please as the ABS is on at the moment

    Sorry if these are basic questions but this is my first older car in a long time but have owned a few Capris so i`m not totally lost with spanners and hammers lol
     
    Last edited: Dec 13, 2012
  6. OP
    North East Car Care

    North East Car Care New Member

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    Location:
    Hartlepool
    Your Mercedes:
    G reg 300E
    Fuel filter change hasn`t made any difference :-(
     
  7. WG M-B

    WG M-B Senior Member Authorised Forum Supporter

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    Joined:
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    Location:
    North west london
    Your Mercedes:
    C63 Wagon in black
    To the side of the battery is a large silver relay. This is the ovp relay,and as previously mentioned its quite possibly the culprit for your hard starting!
     
  8. maska

    maska Senior Member

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    Location:
    Auckland New Zealand
    Your Mercedes:
    E Class


    You Got It RIGHT first time ! :D
     
  9. OP
    North East Car Care

    North East Car Care New Member

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    Joined:
    Dec 5, 2012
    Location:
    Hartlepool
    Your Mercedes:
    G reg 300E
    Cheers, is this relay a straight forward swap or do i have to get one with matching numbers.
    Sorry if this a silly question but i`ve found one on ebay which i was looking at buying to see if i can cure this issue as other than the cold start issue its a cracking car to drive
     
  10. OP
    North East Car Care

    North East Car Care New Member

    Messages:
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    Joined:
    Dec 5, 2012
    Location:
    Hartlepool
    Your Mercedes:
    G reg 300E
    Thanks for the help and advice guys, replaced the ovp relay yesterday and its like driving another car, starts first time and seems much more responsive when being driven
     

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