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R129 SL500 won't start

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Glyn Furlong, May 19, 2020.

  1. Glyn Furlong

    Glyn Furlong New Member

    Messages:
    9
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    Joined:
    Apr 25, 2020
    Your Mercedes:
    SL500 R129
    Hello there.
    I'm quite new to this forum & would be grateful for any help whatsoever.
    My 1992 R129 SL500 refuses to start.
    I've been trying for 3 weeks now but still no joy.
    The car hasn't had a run out for some time due to I'll health but was started up last year a few times by my son and the engine run sweet.
    However when I've come to it this year it just won't fully fire.
    There is spark to all the plugs and fuel is getting through, however there is a strong smell of petrol from the exhaust.
    I'm getting closer to it running as it is now running for 2 or 3 seconds then cutting out.
    There are three lights on the dashboard for ASR, but that's always been on. But there are also lights for seatbelt warning & battery. Even though I've just put a new battery on.
    It's also just started chiming from the drivers seat.
    It wasn't doing this before when it wouldn't start.
    I would be unbelievably grateful if someone could help as at the moment it's the one thing that I'm desperate to sort out as I've never really had time to enjoy the girl through ill health and would love to do a proper road trip in her.
    Thanks so much for your time.
    All the best & stay safe.
    Glyn.
     
  2. LostKiwi

    LostKiwi Senior Member

    Messages:
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    Joined:
    Aug 25, 2006
    Location:
    Midlands / Charente-Maritime
    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    Try helping it fire up with some easy start.
    If it's been longer than 6 months you may have issues with stale fuel.
    Check the fuel pump runs when you turn the key to ignition position (you should be able to hear it).
    Remove the feed from the fuel filter and check for flow (you'll need an assistant to flick the key on/off).
     
  3. Wearsafoxhat

    Wearsafoxhat Senior Member

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    Joined:
    Aug 9, 2011
    Location:
    Sunny Hampshire by the sea
    Your Mercedes:
    05 E55k Est, 99 SL500, A200
    Stale fuel would be my guess too. You say that the plugs produce a spark and fuel is clearly going into and out of the cylinders for it to get to the exhaust.

    I always put some “star tron additive” in mine when it is laid up for the winter.


    Sent from my iPad using Tapatalk
     
  4. OP
    Glyn Furlong

    Glyn Furlong New Member

    Messages:
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    Joined:
    Apr 25, 2020
    Your Mercedes:
    SL500 R129
    Hello there LostKiwi.
    Thanks for your reply much appreciated.
    I'll give it a go tomorrow and get back to you don't mind pal.
    Thanks again.
    Glyn
     
  5. OP
    Glyn Furlong

    Glyn Furlong New Member

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    Joined:
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    Your Mercedes:
    SL500 R129
     
  6. OP
    Glyn Furlong

    Glyn Furlong New Member

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    Joined:
    Apr 25, 2020
    Your Mercedes:
    SL500 R129
    Sorry I also meant to say that I can hear the fuel pump prime/run on the ignition.
    Thanks again.
    Glyn
     
  7. LostKiwi

    LostKiwi Senior Member

    Messages:
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    Joined:
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    Location:
    Midlands / Charente-Maritime
    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    That's good then. Try putting in a new fuel filter. Old fuel can form varnish and gel if left which can gum up the filter. If it fires up well on easy start it's definitely a fuel issue.
    These cars are very hard on ignition systems and have had habit of getting condensation in the distributors. Might be worthwhile popping the caps off and checking the rotor and cap, give them a good spray with WD40 and wipe out again before reassembling.
    If this is a repeated issue remove the cap and rotor, lift out the bakelite shield below and liberally wipe the back of the shield and metal surface of the head with silicone grease then reassemble. Should stop it for a year or two.
     
  8. JuniorMechanic

    JuniorMechanic New Member

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    Joined:
    May 23, 2020
    Your Mercedes:
    w124 230CE
    Hi, had same issue with my 1991 w124 ce. The fuel pump was ok, but not the fuel pump relay. For some reason the fuel pump relay was broken. Put a new one and problem solved.
    Another issue I had and had same symptoms: the fuel pressure accumulator. Located next to the fuel filter and the fuel pump.

    Hope that helps
     
  9. OP
    Glyn Furlong

    Glyn Furlong New Member

    Messages:
    9
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    1
    Joined:
    Apr 25, 2020
    Your Mercedes:
    SL500 R129
    Hello all.
    Thanks again for your time and help.
    I'm gonna try and tackle the fuel system today.
    Hopefully I'll have some good news by the end of the day.
    Thanks again for all the info, it's been invaluable.
    Glyn.
     

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