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1993 500SL - Litany of symptoms - All to do with OVP Relay?

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by Whelo, Sep 12, 2019.

  1. Whelo

    Whelo New Member

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    Your Mercedes:
    R129 500SL / W126 300SE
    Hi all,


    I have a 1992 build (reg '93) R129 500SL (Jap import if that's relevant?) and it has recently acquired a number of irritating symptoms and issues that I would very much appreciate your advice on. I have searched through the forums as best I can and many of the symptoms point to the OVP Relay, but not all, so apologies for a new thread if it turns out I am covering an existing topic.


    Symptoms


    - Odometer & trip now not clocking up miles - Some may say this is great! I had the gears replaced behind the odometer, but no joy - no bits stuck as it is not clicking and trying to move on - it just sits there not moving.

    - Time clock not working - When gears in odometer were changed, the guy said the clock was working fine on his bench. Great, but not working in my cluster!

    - Very high idle in park - up to 2000. It also idles higher than it should when in drive, but with brake pressed - like in traffic. Apparently there is no evidence of any vacuum leaks.

    - Terrifying shunt of power when going into reverse - like there is no control whatsoever over any of the torque. This is a violent lurch into reverse.

    - Very occasionally I have had the ABS / ASR lights up, but really not very often. Turn off car and start again seems to solve it.

    - Battery died quite quickly when not in use last Winter. I mean after 3 to 4 weeks it was dead. Brand new battery.


    Can all of this be related to the OVP Relay?


    I would love to hear from you to see if the symptoms above can all be attributed to the OVP Relay issue or if I am dealing with a couple of seperate issues. I have also read that there seems to be a number of different variations of what type and where the OVP Relay is located in an R129 500SL. Would love to get any and all advice from you all.


    Many thanks in advance for your input...
     
  2. LostKiwi

    LostKiwi Senior Member

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    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    This will be a symptom of the high idle speed.
    These cars have hydraulic control on the gearbox (as opposed to electronic on the later 5 speed cars) so no torque control whatsoever.
     
  3. Richard Moakes

    Richard Moakes Senior Member

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    Your Mercedes:
    1991 R129.066 M119.960; 2005 W164.175 M113
    The high idle sounds like a vacuum leak or idle air valve to me.

    Smoke test of the inlet system would show any leaks.



    Sent from my iPad using Tapatalk
     
    Last edited: Sep 12, 2019
  4. OP
    Whelo

    Whelo New Member

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    Your Mercedes:
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    Thanks for the replies. Mechanic hasn't found any evidence of any vacuum leaks, so I'm hoping to do a bit of research myself first to see what could be happening before I let him loose on it.
     
  5. LostKiwi

    LostKiwi Senior Member

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    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    Is this the K-Jetronic or L-Jetronic engine? You can tell by looking under the bonnet at the back of the engine there will be a half circle cutout in the engine cover if it's K or if it's an L the back edge of the engine cover (filter housing) will be straight.
     
  6. OP
    Whelo

    Whelo New Member

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    Woah... I'm learning new terms every day! :) I have absolutely no idea, but I'll check that out later and update. THanks.
     
  7. OP
    Whelo

    Whelo New Member

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    Hi again. Could you please point me in the right direction based on the photo below? I'm assuming it's a K? Thanks.
     

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  8. OP
    Whelo

    Whelo New Member

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    Your Mercedes:
    R129 500SL / W126 300SE
    Incidentally, below are some more pictures of where I believe the OVP Relay and MAS relay are located? The OVP is the one with the red fuse isn't it?
    When I opened up this section, I noticed the frayed wires and thought aha! this must be the cause of all of my problems, but it seems those cables have been disconnected from whatever they were delivering. Anyone any idea what they would have been for?
     

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  9. LostKiwi

    LostKiwi Senior Member

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    K-Jetronic.
    The rear edge of the air filter box is curved around a fuel distributor.
     
  10. OP
    Whelo

    Whelo New Member

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    Thanks for that. Is one type more prone to something than the other?
     
  11. LostKiwi

    LostKiwi Senior Member

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    K is a mechanical injection system whereas L is electronic.
    As mine is L I don't have experience of K.
    One thing you may want to check is the condition of the wiring harness on top of the engine and particularly the throttle body harness. 1992 was the start of the period where they self destructed due to insulation biodegrading faster than expected. Check any wire going into . a connector If wires are exposed it's knackered.
    This was my throttle body harness. It ran well but would throw random errors with ASR.
    20170806_153911.jpg
     
  12. Richard Moakes

    Richard Moakes Senior Member

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    That wiring looks like it has overheated and melted, rather than the usual biodegradable loom issue?


    Sent from my iPad using Tapatalk
     
  13. LostKiwi

    LostKiwi Senior Member

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    It may have biodegraded then got hot of course...
     
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  14. rayhennig

    rayhennig Senior Member

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    Your Mercedes:
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    The cars with the K-Jetronic never suffered the biodegradable wiring problem.

    However, wiring in general and connections should always be checked and cleaned as necessary. I always try to clean contacts whenever possible.

    RayH
     

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