The timing issue is quite simple. Bosch added a hall effect "nipple" to the governor assembly to permit dynamic timing, and it just happened that the "nipple" goes past the point where they could put the pickup sensor hole at 15 degrees after TDC. The pump actually operates exactly like earlier ones. This was done in 84 or 85, as some later W123 models have the same setup. Some W123 turbo IPs were assembled with the injection pump cam 180 degrees out, but none of the 603 pumps have this quirk, so if it's set at 24 degrees BTDC by drip method and 15 ATDC by hall effect pickup, the timing is fine.

That IP with no hand pump can take FOREVER to purge when empty, much worse if you changed the fuel filter as well. The only real cure is to crank until it finally gets the air out, and if you have fuel and air coming out of the injection lines, it's purging, keep cranking. It's rather unlikely you will get it to start on one battery charge, and if the suction side lines are leaking air in, it won't start until you replace the lines. It will run with leaking suction lines, but if you ever get enough air into the pump to prevent easy starts, it won't prime well enough with the air leaks to ever start.

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!