My first inclination would be to pull all of the injectors and have them tested. Second, pull the injector pump and have it tested. My 1650 and 1955 never seemed to require any special bleeding sequence. If the injectors and pump are up to specs, I'd do a compression test. Doesn't take much of a loss of compression to make a hard starter out of a diesel. An air leak in the fuel system, could cause you problems, too. How long has it been since the sediment bowl has been removed from the fuel tank and cleaned? Unscrew the fitting out of the bottom of the tank and check out the feed tube/s. Sometimes the simplest things cause the biggest headaches. Make sure you don't have a slug of water in the bottom of the fuel tank.