Pull the right valve cover and see if the timing chain is still there. If so, set engine to TDC on #1 and see what the valve timing is. If it fires up the intake, make sure the rotor isn't broken.
Also, check for a clicking sound from the injectors, and make sure the fuel pump is running.
6.4 volts isn't enough at the fuel pump, it requires 9. Should run for a second or so when you switch the ignition on, and then while cranking.
You can also check by pulling the relay in the box under the passenger side kick panel -- top one on the front set. Bridge the terminals labled 30 and 87, key on. Pump should run. If it doesn't, and you don't have good voltage, pull the next relay down and bridge it the same way. If pump runs, replace second relay.
If the pump does run, replace the first relay.
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!