It's not the cold start system (and you do have a cold start valve), it's an oxygen sensor or warm running mixture problem. In closed loop mode you are WAY rich, but this could be a number of problems.

You need to check fuel pressure, the voltage to the EHA (EHC in brit-speak), the duty cycle on pin #3 on the diagnostic connector, and the oxygen sensor.

This will tell you what is wrong -- bad EHA, bad fuel pump, bad pressure regulator (check for fuel in the vac line going to the valve cover from the pressure regulator), plugged return line, toasted engine control box, etc.

You may in fact have a defective fuel distributor -- running way rich with black smoke is a clue. Only cure is replacement. Also not likely if it only does it warm -- defective fuel distributor runs way rich cold too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!