any ideas what the cause is ? 55 plate primastar 88000 miles?

my 2005 nissan primastar has started cutting out at speeds of 25mph and above, the engine makes a very loud rattling noise and black smoke comes from the exhaust, slows right down and cuts out, i have to pump the primer by the fuel filter and up it starts no problem, half a mile down the road it happens again, no management light comes on ! the noise sounds really loud, rattling and banging,
had the fuel filter and fuel lines changed and sender pump in the tank checked, all fine on tickover but when accellerating the problem kicks in again.