[W126 Coupe] 380 died :-(

[Mister McGoo]

Ingrid,
When you jump-started the car I assume that the warning lights came on when the key turned to "on".  After starting the car with the engine running, did you check the battery with a voltmeter?   It should read between 13v and 14v in which case the alternator is working fine.  If not, likely your alternator is toast and you drove the car 100Km on the battery (which is amazing).  If the battery was nearly flat the momentary current interruption of the turn signal could have killed the ignition. 
Like I said, a bad fuel relay, ignition module, coil etc, shouldn't have prevented the starting motor from turning the engine over... wouldn't start the engine mind you but it would have turned over.  Have the charging system checked.
The alternative problem could have been much much worse.
best wishes,-Al  

Date: Mon, 7 Nov 2011 05:13:41 +1100
From: ingrid at pcutechnology.com.au
To: eelploot at hotmail.com
Subject: Re: [W126 Coupe] 380 died  :-(


  


    
  
  
    Hi Al,

    Your description of what happened is correct.

    

    I'd just driven 100 km (63 miles) from work and turned off the main
    street. The car died.  The load added to the alternator was the
    indicator switch.  No warning lights came on, I turned the ignition
    off when I'd pulled the car into the kerb.  

    

    I turned the ignition on again to close the windows and sun roof. 
    Still no warning lights.

    

    Yesterday my brother and I worked on it.  You're right, the fuel
    pump and the fuel pump relay are not the issue - we bridged the
    relay, the car still wouldn't start. The fuel pump is OK. The relay
    itself looks sound - no dry joints, no signs of burn. 

    

    We were able to jump start the car.  The battery appears to be, in
    your words, seriously run down. Also, when I revved the car, the
    battery charge dropped and didn't recover.  

    

    So, I shall drop a new battery in & get the local auto
    electrician to check the alternator.  (Just in case - the battery
    was elderly, but I want to be sure that it's not a symptom of other
    problems.)

    

    Once again, thank you.  

    Ingrid

      Cooma, Australia

      380SEC

     

    

    

    On 06/11/2011 16:32, Mister McGoo wrote:
    
      
      
        Hi
            Ingrid,
        

          
        A
            couple of [late] thoughts considering your brief description
            of what happened………
        

          
        I
            assume that you were driving along OK, and the engine quit.
             Upon trying to re-start, the engine would not turn over,
            but the solenoid clicked. (assuming that the click was
            coming from the starting motor.)
        

          
        Did
            any warning lights come on at the time when the engine quit
            or did you switch the ignition off as soon as you noticed
            that the engine had stopped running?  
        

          
        The
            battery is likely OK.  You can confirm that by trying the
            power window, turn signals, power seat or wiper to see if
            they operate reasonably normally.  (a battery can test 12V
            but short out when loaded.)
        

          
        The
            alternator is likely OK because otherwise your battery would
            have been seriously run down plus you should have had a
            warning light on.  You can drive on the alternator even if
            the battery is totally dead but you must have one or the
            other.  The exception may be if you suddenly add load to the
            alternator (with no battery backup) such as putting your
            high beams on.  This will interrupt sufficient power to the
            ignition momentarily and the engine will stop.
        

          
        Unless
            you have had trouble with the starter, the starter is likely
            fine also.  The engine was running.  It didn't stop running
            because the starter suddenly went bad.  With the car running
            the starter is "out of the loop" and obviously it HAD worked
            just fine in the very recent past.   However, a starter
            problem is still not ruled out but it would not have
            anything to do with the engine quitting.
        

          
        If
            the ignition module fails that would not prevent the starter
            from turning the engine over.  
        

          
        Nor
            would a coil or fuel relay failure prevent the engine from
            turning over. 
        

          
        So
            first I would use a known good battery in top condition to
            see if the engine will turn over.  Before trying to start
            the engine when you turn the ignition switch on, do the dash
            warning lights come on and will the turn signals and wipers
            work?  If nothing responds and the starter won't engage, or
            even if only some things work, the fault is possibly the
            ignition switch itself.  Most things go through the ignition
            switch including the starter and ignition system.
        

          
        (Also
            try starting in Neutral instead of Park.)
        

          
        If
            everything works (lights wipers) except the starter, watch
            closely to see if the dash lights dim when engaging the
            starter.  If so, the starter motor is trying to turn the
            engine but can't.  Keep trying and the starter will get hot.
        

          
        Time
            then to consider Plan "B".
        

          
        But
            so far, from 5000 miles away, I'd say the ignition switch is
            suspect.
        

          
        Al
        

        
        

        

           

            
          
            
              

                  My 380SEC died as I was driving home yesterday
                  afternoon (fortunately, I 

                  could pull off the road, AND I was within walking
                  distance of home ).  

                  Preliminary investigation suggests electrical and/or
                  starter motor - 

                  when I turn the ignition key, I here a series of
                  clicks, but nothing 

                  further.  We checked the battery with a voltmeter -
                  full charge, drops 

                  slightly when the ignition is turned.

                  

                  Any ideas?

                  

                  Cheers,

                  

                  Ingrid

                  Cooma, Australia

                  380SEC

                
            
            

            

            
            

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