I have to guess that you have a carbureted gasoline type truck. I'd say that the oil leaking from the pump (which I assume is on the engine block) is because it has a leaky gasket or the pump is worn out and leaking oil from the inside to the outside of the pump. if you have this type of pump, probably the rubber hose is a vent hose put there to keep dirt and water out.
yes its a carborated engine .its either the fuel pump or a pressure regulator. its attached to the bottom of the intake manifold. . it runs great other than that oil leak. i tried to plug it off and it just blew the line off that i put on it. also it runned bad until it blew it off. ??
same thing here! I guess the oil galleys in the block get clogged and spit out oil i was just told to get a 5 foot hose that is oil compatible and switch out the old one and run it back down the oil dipstick tube. its working so far knock on wood