You can get one of these from most any auto parts store, this happens the be from Napa. I usually just shove a Phillips screwdriver into the plug wire.

Your way was maybe a bit clumsy but worked fine and caused no real danger. If you had left the plug too close to the hole it came out of, you could have had a bunch of mini explosions each time it fired.

I'd check all of your battery cables and try swapping the battery from the other car. If MB's is too far gone, it will put too much of a load on the jumper cables and the voltage drop will give you a weak spark.

Michael

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Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120