Getting air in the fuel system on my '92 dodge 3/4 ton 4x4 w/cummins. I've replaced filters, water in fuel sensor, put on new fuel pump (old one was original and weak). Now I have a leak above the fuel filter somewhere. Is there an O-ring above the plate over the filter? I found this loose one time when I changed the fuel filter. Is there a schematic available for this engine and fuel system?

Thanks