Escort 1.8 D fuel woe?

The van had started to drive ok then loose power run ok and loose power regulary, somtimes nearly cutting out, so i have changed the fuel filter and now it will not start, i have tried priming it but that now doesnt seem to work it did before. it cranks over but does not fire up at all. it all seems air tight just no fuel it has plenty in tank and filter. Any Help would be appreciated and anyone who can explain the bag trick???