Turn the screw the other way in small increments until you get very close to 50% and it's set correctly.
It will go rich every time you adjust it since you have to press down slightly to turn the screw -- this presses down on the flow sensor and adds more fuel. It will return to "normal" running state in a few seconds after you lift the allen wrench.
Check the wires for the O2 sensor heater, too, it should heat up faster than the 60C switch, I think.
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!