Fuel Leak (Breather?)

[Big MAK]

What is this... and why is it leaking? Started as a very minor drip several weeks ago but now quite a bit of fuel runs out.

 

[Cummins12V98]

Filling your rig to the top?

 

[Big MAK]

Filling your rig to the top?

Does it when it's nearly empty or full; no difference.

Inside of the fill area is bone dry; no spillage.

It's spurting out of that breather looking thing I'm trying to sort out why it's getting progressively worse.

UPDATE:
Observed there is a ball valve about 3.5" deep into the neck - if you pull the fuel nozzle out too quick the fuel in the neck of the nozzle can collect above the ball and never go down. Tight fit! I put a screwdriver in to push the ball down and let the fuel drain into the tank.

Still dripping regularly out the breather, I don't think it was leaking from above the ball valve - just noting it because I don't want that fuel getting dirty.

Ran truck thru the wash and dirt + water on my fuel cap.

(catch that?)

Anyone have issues using a fuel cap to prevent dirt and water from entering the fuel?

(ps: if they don't prevent fuel and water from getting in the fuel why does FCA put them in for shipping?!!)