Your only fuel lift pump is on the driver's side of the engine block below the fuel filter. You don't have, never will have nor ever had a pump in the tank. Your either sucking air (Joe G's fuel writeup on how to fix) or your timing has slipped or very low fuel pressure. Either one can cause your issue of gray smoke. You can suck air and never have a fuel leak. All it takes is a crack so small you barely can see with the human eye. What tests have you done to be sure you are not sucking air? Yes, you do need to check fuel pressure. Low fuel pressure can cause bad running issues also. Low pressure can be as simple as filters (both main and pre) needing replaced, bad lift pump (rarely), bad overflow valve (common) and some other things. Your 12 valve fuel system is completely different from a 24 valve. About the only similarity is that both use diesel fuel.
'96 Dodge 3500,KDP killed, boost-pyro-trans temp, not stock anymore
'01 Dodge 2500 4X4, EC, LB, 6 speed, FP-pyro-boost,
'97 Chevrolet Suburban, K1500, 4.10 gears