fuel pump problem, i think

hi there, having problems with starting my 90.
is an a reg with perkins 3l turbo retrofit in 99. its trying to turn over but lacks the fuel i think. having previously sorted an earthing fault i reckon its not that. on manually pumping the button on its top can hear flow but nothing from bleed screw.
the system may have 2 filters by the look, line comes from tank to glass dome, can see diesel trying to flow here, opening the wingnut beneathe leads to diesel leak, it just doesnt seem to want to pull above this.
any ideas?
the line from this goes to the said pump, which has a black fuel filter beneathit. with a line out to throttle, then onto engine.
cheers loads

Check the filters, a filthy filter can reduce flow to unusable levels.

Go to the output end of the lift pump, and disconnect it, pump the fuel manualy, do you get fuel? Move the engine one little blimp on the starter and try again (incase lift pump sitting on wrong side of cam). If no sucess its a lift pump problem, if your getting bags of fuel then its an injector pump problem or pipe work/filters after the lift pump.

cheers mate, will try tuesday when off work. heres hoping!