1987 ford econoline cube van 5.8 liter fuel pump

hi i am looking for a diagram of the fuel system i think my carb is in need of rebuilding but might be my fuel pump i cant find it .anyone have diagram?also along the rail there seems to be another kind of external pump or helping unit but is not hooked up but makes a noise.the truck would start then bog out on me after about 20 minutes i would start again and 5 minutes later the same thing PLEASE SOMEONE HELP:banghead: :crying: :shakehead