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Discussion Starter #1
I shouldn’t even be admitting this but as I have gotten older I figured out that admitting foolish mistakes is healthy.
OK it was Sunday and I was out in my 71 280S. I left the trunk open for several hours at my RV site and when it was time to go home the battery was dead. No problem, I just removed the battery from my RV and dropped it in for the ride home. By the time I pulled into my driveway the car was running horrible. Then the fireworks started, as I looked out of the windscreen in horror a hole emerged in the newly painted hood and sparks shot up like a roman candle. I opened the hood and saw the positive battery post welded to the underside of the hood. The temporary battery was not the right size and it made contact with the hood melting off into the hood.
Besides having to have the hood repaired what may have happened to the car? I had recently installed a Hot Spark electronic ignition with a 50K coil. I started it to get it under cover then shut it off and covered it up till later. It ran like hell for that short time.
 

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73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
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Wow!!! You might have damaged to Hot Spark system, or the ECU. Sorry to hear about your troubles
 

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Discussion Starter #3
Thank you for your comment but the ECU was removed. No need for this expensive unit with a electronic ignition upgrade
 

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73 280SE 4.5, 71 300SEL, 03 BMW Z4, 72 Fiat 850, 80 Triumph TR7, 85 Porsche 911
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Wait a sec - I should have been more thorough in reading your post. Your 280S has a carb'ed engine, yes?
 

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Discussion Starter #5
Yes a 1971 280S Carbed unit

Yes I have the duel carbs. I believe they are Mercury’s. I have suspected problems with the carbs since I first started the car. I wanted to rule out ignition problems so I did away with the ECM by installing the electronic ignition and coil upgrade from Hotspark. I was pleased with the results. The mechanical advance in my aluminum distributor was sticking but once I cleaned up the counter weights the car ran much better. Still stumbling at start up and much feathering of the throttle is necessary to keep it from stalling out. Timing is dead on at 6 deg BTDC at idle and around 37 deg at 3000 rpm. Timing returns to 6 deg immediately upon release of throttle. This makes me feel confident that the ignition problem is solved and I now have to turn my attention to the carbs. I am not much of a carb guy so I am forecasting a big repair bill.
 

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'72 250C, '74 280C, '85 500SEL, '81 300CD.
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Yes I have the duel carbs.
This mis-spelling is sooo true! When they are right, they are right. When they are wrong they are so wrong! I fought a pair of twin Solex carbs on my 220 for years before I converted to fuel injection.

Easy enough to do on the 220 (M115), not so easy on the 280 (M129, I believe).
 
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