300SL R107 1986 - NOT STARTING IN THE COLD - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 01-06-2015, 12:08 PM Thread Starter
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Date registered: Aug 2013
Vehicle: 1986 Mercedes 300 SL
Location: London
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(Thread Starter)

London, England - 300SL was driving perfectly over the summer, when I was using her regularly and was decent weather. In late November I was away for 10 days on vacation and when I returned I was expecting the battery to be flat (which it was). However quick jump start and the car was going again, but i failed to take her for a long drive, which I should have done.

Few days later the car wouldn't start and the battery had gone flat again.
I connected the jump start cables to another car and mine still wouldn't start.
After about 15 minutes on constant attempts to start the car, it gradually showed signs of waking up and very slowly the engine kicked in, more and more. Eventually I got the car going, and took it for a long drive (1 hour), enough to charge the battery, I would have thought?

Next day, car doesn't start again.

I have already disconnected the battery and charged in my house, but once connected again, it doesn't have enough power for 15 minutes worth of turning the ignition.

So, can I assume its nothing to do with the battery, as even when I have the jump start cables it doesn't start for a long time?

I have a new alternator fitted this year.

The only thing I can think of is that the distributor cap has moisture in it, as this has been a problem in the past.

Maybe I just need to drive her to Scotland and back?

Someone suggested gas line antifreeze?

Any thoughts, experiences or suggestions would be most useful.


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post #2 of 4 (permalink) Old 01-06-2015, 06:09 PM
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Sounds like a fuel system problem - accumulator, filter, pump.
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Chuck Taylor
Falls Church VA
1998 SL500
1959 220S
1970 280SL
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post #3 of 4 (permalink) Old 01-07-2015, 05:46 AM
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Vehicle: 1968 250S, 1991 300se, 1998 SL500, 2x 1977 450SEL 6.9. Past MB's; 300SD, 300E, 300TE, 190E, ML420
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have your battery tested, it may be gone. though 15 minutes of cranking is a fairly long time.

then be methodical. check your ignition system out. if you suspect dist cap moisture, then that is easy, start there.

PS, the R107 forum is probably more knowledgeable about your car.
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post #4 of 4 (permalink) Old 01-07-2015, 03:36 PM
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if it was a usa model , i would say that when you jump start the car , you blow the 10 amp fuse in the overload protection relay .this make the car hard starting due to no electronic control of the cis .
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