No, it is connected to a tube inside the tank that squirts oil where you can see it when you remove the oiltank cap. Its outlet is above the oil level and therefore wouldn't drain anything.
So you unscrewed "J" from the tank?,, If there is oil left in the tank, it should have come out. It may be possible that there is so much muck that it is blocking that opening. Conways sells a "manhole cover" that you can install in your tank to make a thorough cleaning possible. You would have to do a lot of dismantling to do the cleaning.
Have you tried sticking a stiff wire in the "J" hole to see if it is blocked? Maybe what appears to be an oil level ion the tank is just shiny sludge on the bottom. Try probing it to see if it is a level or a sludge layer.