Hi, Paul,
Your problem reminds me of the trouble I had with my 230 SL when I first bought it.
The fuel return line had rusted from the inside and pushed all the debris into the tank and blocked the port on the flower pot.
The tank had to be cut open and cleaned out to cure the problem.
If its the coil, you need the Bosch one with the red label (MB 000 158 2703 Bosch 0 221 119 030) with a matching 1.8 ohm ballast resistor with a red band( MB 000 158 1745 Bosch 0 227 901 014).
Naj