how can i fix my movano 2.2 ?

i have a 2003 movano with a 2.2 renault engine had it service and it start to get an air lock in the fuel filter, the problem has go worse of the last couple of month. i bleed the top of the fuel filter and turn the key on but not starting it and you can here the fuel come down the pipes and then it stops. after about 20mins it will start