iveco euro cargo tector wont start first thing help?

Hi I have a 13.5 euro cargo tector it wont start first thing it takes about 15 secs before it kicks in it turns over fast enough but seems like it is not getting fuel fast enough even if i hand prime it still the same i have had the injectors checked ok I fuel filter pump no go it killed one of my batteries all new now still the same I thought fuel might be leaking back to tank so put non return valve on still no good if any one has any ideas please before starter and more battiries go thanks all work done in iveco dealers they dont know.