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500SL Engine Miss

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by mikemartin1939, Nov 29, 2012.

  1. mikemartin1939

    mikemartin1939 Member

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    Your Mercedes:
    500SL/1991/8 cyl- SL500/1999/8 cyl
    1991 500Sl that after about 15-20 miles starts to hiccup. Slow at first but gets progressively worse. Added fuel dryer to tank but it made no difference. Seems as if the problem is heat related. Any help would be greatly appreciated.
     
  2. WG M-B

    WG M-B Senior Member Authorised Forum Supporter

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    Your Mercedes:
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    Sounds like moisture in the distributor caps. Very common
     
  3. Fleetwood

    Fleetwood Senior Member

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    Your Mercedes:
    2005. SL350
    I second the moisture in the dizzy cap

    Remove the caps and give them a good clean, you should be able to see if there is any tracking of the spark

    Check for cracks and replace if there is any
     
  4. OP
    mikemartin1939

    mikemartin1939 Member

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    Your Mercedes:
    500SL/1991/8 cyl- SL500/1999/8 cyl
    I have worked my way to the dizzy caps, right and left. Not much slack in the plug wires so should I just pull them straight off to get the caps off? Anything to look out for in the cap removal after I loosen the 3 allen head bolts?
    The plug wires at the caps and where they rub against each other look as if the might have some fine white ash-like powder where they are in contact with each other. Going to check it after it gets good and dark to see if there is any arcing.
    Thanks for all your help.
     
  5. Alex Crow

    Alex Crow Senior Member

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    Your Mercedes:
    W169, W124, w202, W203, KTM 250 EXC, VW T25 camper and a Polo in a pear tree
    As above +3

    If you do find moisture in them, but they otherwise look OK it is your lucky day.
    Dry them out properly - and a little cheat - spray liberally inside the cap and the arm and back plate with silicone spray, it works wonders.
    I would not worry so much about the leads at this point, they cause little trouble on these in general.
     
  6. OP
    mikemartin1939

    mikemartin1939 Member

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    Your Mercedes:
    500SL/1991/8 cyl- SL500/1999/8 cyl
    Caps had no moisture inside or any apparent tracks. All interior electrical contact points on both caps and rotors are very badly pitted and burned. Ordered new caps and rotors and will advise of results after replacing and a good long test drive.
     
  7. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Do spray the new ones, silicon is very good and elecrically perfect, it will stop the tracking, do the caps as well
     
  8. lanciaman

    lanciaman Senior Member

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  9. television

    television Always remembered RIP

    Messages:
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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Yes and perfect, the coating electrical resistance is not measurable
     
  10. OP
    mikemartin1939

    mikemartin1939 Member

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    Your Mercedes:
    500SL/1991/8 cyl- SL500/1999/8 cyl
    Received the new caps and rotors 10 minutes after my last post. Replaced all, sprayed silicone and did a 31 mile test drive. Put my foot in it numerous times without a hiccup. Don't want to get too cockey but it looks as if the problem may be solved. Thanks too all for your assistance and confidence building.
     
  11. lanciaman

    lanciaman Senior Member

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    E220 Cabrio (A124) - 1994
    Malcolm, one thing. Light or liberal coating, and how often?
    thanks
     
  12. jonthetourist

    jonthetourist Senior Member

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    Your Mercedes:
    1991 SL300-24
    I know it was addressed to Malcolm, but I would vote for very September, just before the cold and damp sets in.

    Jon (fellow sufferer)
     
  13. lanciaman

    lanciaman Senior Member

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    Your Mercedes:
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    Thanks Jon. I love the way a £400 cap and rotor set counts as a consumable!! Or £250 if you get from ECP...
     
  14. OP
    mikemartin1939

    mikemartin1939 Member

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    Your Mercedes:
    500SL/1991/8 cyl- SL500/1999/8 cyl
    The new cap and rotor pair that I got on Ebay was $178.60. Manufacturer was Bremi of Germany. Perfect fit and operation.
     

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