fuel problem

hi guys. im having fuel problems. ive a 96 disco and it started running sick today. its down on power. wont rev out. wont rev over 2000 revs at times. i took fuel filter of to replace it and found it was only a quarter full. thought maybe lift pump so replaced it but still same. took fuel pipe of at fuel filter housing and seems to be plenty of fuel comin out. anyone any ideas?

Thanx

Petesy

check sediment bowl right hand side just infront of fuel tank , dont just remove drail bung , undo smll bolt on top anr pull off bowl and clean it out , refill with clean diesel and try it , may need to reblead at lift pump