2.5di refittet engine trouble starting

[Arctictransit]

I recently did an engine swap to a 1986 2.5di with a Lucas Cav. I changed the timing belt as well. Im having trouble firing it up again refitting. I can have bled my eyes out, but its not catching. I can get it to run if I pump the prime pump on the fuel filter. Air, bad fuel flow or dead pump? I cant seem to nail it down. Any help or thoughts appreciated.