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Starting problem

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by MarkyBoy, Nov 5, 2012.

  1. MarkyBoy

    MarkyBoy Senior Member

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    Hi all, I have a 1998 C250TD that has developed a worsening intermittent fault on starting... Essentially when you turn the key the engine just clunks (it doesn't turn over), then when you try again the engine will start normally. This clunking can happen once, twice or sometime three times before starting or it will not happen at all and the car will start first time... Any ideas what it could be, perhaps the starter motor is sticking?... Any advice welcome!
     
  2. television

    television Always remembered RIP

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    Your Mercedes:
    2002 SL500, 216 CL500, all fully loaded
    Either a low voltage battery or the starter motor failing,,,just by putting a voltmeter over the battery terminal and measuring the voltage when cranking should confirm it,,,it should not drop below 10volt
     
  3. OP
    MarkyBoy

    MarkyBoy Senior Member

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    Thanks Television, I just tested and the battery remained at about 10.3V... The car actually started first time, four times in a row yet earlier this morning it just 'clunked' three times and started on fourth! Do you think it's the starter motor then?... If so, is there a test I can do to verify the starter motor has a problem?
     
  4. wireman

    wireman Senior Member

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    Your Mercedes:
    nice 201 2.5D 1993 & very nice 129 SL500 1994
    Check the integrity of the battery leads and engine earth strap.
    Measure for a voltage from engine to battery negative while cranking, anything more than a volt or so means a poor connection. Check the battery to starter lead like wise.

    Do the warning lamps dim when you try to crank it?
    If the warning lamps are not dimming when the starter is engaged and it does not turn my immediate guess is that the contacts in the starter could be getting very tired.
     
    Last edited: Nov 5, 2012
  5. OP
    MarkyBoy

    MarkyBoy Senior Member

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    Thanks Wireman... Voltages all look okay and lights do not dim on the dash when cranking.... If contacts are worn, does that mean a new starter motor? Assume I am not competent to strip it down!
     
  6. wireman

    wireman Senior Member

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    Your Mercedes:
    nice 201 2.5D 1993 & very nice 129 SL500 1994
    Probably the best way is a re-conditioned unit, it might be possible for the adventurous to do it themselves.
    If you have a half decent auto electrical outfit in your parish they may be able to fit just a new contact or solenoid assembly to your starter at somewhat less cost.

    10v is awfully low for the battery voltage, it should be at least 12v, do ensure you have a good battery and alternator before you splash out on the starter motor.
    When running you should have between 14 and 14.4v at the battery terminals, with all the big loads on, i.e. headlights and heated rear window it should remain at 14v or more.
    Once there is a little charge in the battery it should hold at least 12v over night, given the 10.3v reading I suggest that you put it on charge for a good few hours and see if that helps.
     
    Last edited: Nov 5, 2012
  7. OP
    MarkyBoy

    MarkyBoy Senior Member

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    Great advice Wireman... I'll try doing a charge on the battery first and see if that improves... Could be the reason actually as it the problem does seem to be worse after the car has been standing overnight... Which may suggest an earth leak I guess although that looked ok when I checked.... Anyway, will do that first and if no better will look for a starter motor.
     

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