2000 f250 7.3 sdp,won't start,have had trouble starting for some time,glow plug are working.when it would start,it would run rough for a few miles with no power,like it was running on 4 cyls,then,like you flipped a switch it would take off and run 'normal'.I changed fuel filter,put a new fuel pump on,now it won't start at all.the fuel filter can is filling up.