My next step would be to prime the fuel system by inserting perhaps a boat bulb fuel primer about $4.00 or so just ahead of the perefilter and pump away. Maybe also remove your return line and catch the fuel and look for baubles. Once primed reconnect the tank return line remove the pump bulb and reconnect the supply line maybe even change the prefilter? Now only the injector lines need to cllear of air. Loosen the hard lines at the injectors and crank until you see diesel come out then retighten. Now crank away it should go after awhile.