BenzWorld Junior Member
Date registered: Jul 2012
Vehicle: 1969 Mercedes-Benz W108 280SE
Location: Johannesburg South Africa
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Two problems, one spark plug...
Today marked the day that the W108 280SE ran on all six cylinders like never before. I'm struggling to get the car to run on all 6 cylinders even though the compression is excellent and all cylinders are receiving fuel. This obviously points towards the spark and this was confirmed by replacing all the spark plugs with OEM Bosch ones.
The first problem is that the engine runs very well when I pull all the spark plug leads from the spark plugs and hold them close to the spark plug and run the engine like that. It fails to run on some cylinders or not very well when I engage the lead coupling over the spark plugs heads. Am I correct in saying that the spark is too weak within the cylinder, from the spark plug, when I engage the coupling of the lead and by leaving a gap between the lead and the spark plug, the arcing over to the spark plug increases the spark strength inside the cylinder? If this is the case, any recommendations?
The second problem is that the mixture is too rich. I have turned the adjustment screw on the back of the injection pump anti-clockwise 4 times already, each time with the engine off and then restarting,shutting down and turning it another notch. I.e. I performed this procedure 4 times and the engine still runs too rich. My manual says that I should not turn the adjustment screw more than 4 times in either direction. Does that mean that I can only turn it 4 notches at a time or is that the overall number of times it can be turned? The spark plugs are covered in black carbon deposits and it is quite an irritation to have to take them out and clean them ever so often. I keep on cleaning them up in hope that the problem above would be resolved.
Thanks in advance,