2.5 v6tdi wont start on a hill any idea?

i have a 2.5v6tdi and if it is parked on a hill facing up over and its been stood for over a hour and you try to start it it cuts out after a couple of seconds it takes about 5 mins for it to start it seems like the starved of diesel and it geting to the point it does it on the level aswell i have changed the diesel filter so for can anybody help please thank you