Issue leaking Diesel.

[Tano]

So, I am new to the forums as you may be able to tell. I recently bought a 2001 Chevrolet Duramax 2500hd 6.6l turbo diesel with 133k miles, cold air intake, and 5'' straight pipe for $7500. Here are pictures of the truck

But to cut to the chase. Today I filled up at the gas station, and noticed and steady drip coming from behind the fuel spout. and sure enough, it was diesel.
So I looked further into it, and I found a small brass nipple that had no hose attatched. I have no clue what should go there and can not find any loose hoses or anything of that nature. Here are pictures of the brass nipple. If anyone could give me their suggestions or point me in the correct direction it would be greatly appreciated.

 

[Lofti7]

someone had a bulk tank plumbed in before you bought the truck you just need to plug the hole and your set
Welcome to the site

 

[chevyburnout1]

May of had an AirDog or Fass fuel pump installed on it at one timel. Both of those pumps have a return that usually gets plumed into the filler neck.

 

[Dozerboy]

X3 regardless having that fitting pointed down seems like a bad idea. I would flip it up top then cap it off.

 

[kking]

That's a steal for that truck, maybe I should have flown to Texas to buy a truck!!:thumb:

 

[Ne-max]

Could have had a transfer tank in the bed for filling up but I am guessing a lift pump cause of the direction of the fitting.