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Vintage Cars/1983 Mercedes 380sl

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Expert: Ron - 11/2/2009


Question

1983 Mercedes 380sl
QUESTION: I last came to you in August, I got the car running, then it started running rough like before. Changed the spark plugs, dist cap & rotor, started and ran for 150 miles. Then the car just stopped running going down the road. Towed it home. NO spark at all. Changed the coil, still no spark. checked around for vacuum leaks, found non, but the black grommet around the green wire to the ignition control unit was shot. This wire runs to dist. Is there a check for this piece or would it just die ????
Thanks in advance

ANSWER: I would suspect a short to ground?? Was the wire bare, or in contact with metal that would ?may have caused a short???
No test I know of, do you have spark now??

---------- FOLLOW-UP ----------

QUESTION: The piece I'm refering to is part # 002 545 26 32 (Ignition Control Unit)
It's located on the fender wall in the engine compartment. Single green wire from unit goes to distributor,(this wire has  contector attached to it) black contector has 4 plugs (these wires are Black, Brown, Green with Yellow stripe, Red with Black stripe), these go to coil and a computer plug (9 pin). Does this control electrical charge from coil to dist. ???
I have no spark at all from coil to dist to spark plug wires ???
The motor turns but no fire...I sent picts don't know if they took or not
Thanks, Alan

Answer
The ICU is really just a switchbox (think of a transistorized relay) that prolongs the life of your ignition points by sending the low voltage signal to them instead of the 12V that'd otherwise be used to power the coil.
A 12v bulb on the wires that connect to the coil. It'll flash during cranking if the box is good. If not, it won't. That simple.  Just make sure all connections have continuity.
I assume you have checked points gap ,timing And that green wire from distributor is properly connected. Coil could also be faulty.
Leaving car in run position ( key on) is the way to kill an ICU.

If your coil is after market , make sure it is still good

Ron

Expertise

I can answer questions on W114/ W115 /W(R)107/W123/W126 Mercedes models 1967-1985. I have rebuilt many of these cars and have problem solved many issues. I have access to much of the technical data and have deailed instructions on fixing the most common issues. Vintage US 1950-1989 and other foreign cars as well If you are going to ask me about car value, please provide ample information on service history, rust issues, and current "needs". Pictures are helpful. Disclaimer on value - I can only give you data on what the market is bringing, and may not be what you want to hear!

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Maintain, restore vintage Mercedes (W114/W115 /W107/W126)

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College Graduate. Self proclaimed and taught Mercedes shade tree mechanic.

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