Is that the passenger side right down near the passenger manifold? If so its the fuel bowl drain tube. If you look at the fuel bowl theres a yellow lever, first off make sure its closed all the way, secondly open it and close it real quick and see if some diesel comes squirting out of that tube you identified. If it is you need to reseal the fuel bowl drain lever. Heres a link to the orings you need Ford 7.3 Diesel Fluorosilcone Drain Valve O-ringsOn my early '99 work truck there's an open-ended drain tube coming from the fuel system/filter housing on top of the engine. There's a steady drip when the truck is idling. Does anyone know what this indicates? I thought it might be the fuel filter need changing. I did that but it still drips. I haven't had to work on this truck much so I don't know the 7.3's that well. I'm more into the 6.0's.
You can see the wet end of the tube in the upper center of the pic. It comes down in front of the cross-member and the fuel drips onto the long tie-rod end.