Fuel Pressure?

A day ago I noticed diesel was leaking from my Davco fuel filter and the fuel level was abnormally high (shop replaced it fairly recently). It seemed to be coming up all around the housing, made me wonder if the oring wasn’t seated properly. Bought a filter and the removal tool. Problem is, when I drain the diesel down to a level just below the lock collar, when i pop off the top cap, it immediately starts filling back up with diesel to the same high level. I think I probably drained 2 gallons of diesel before I gave up. I can’t even take the housing off

I did discover that the vent line was disconnected from the little filter thing on the passenger side tank.

 

The fuel fills back in with the truck off, forgot to mention that

 

I tried draining it with the cap off. It just flows out of the valve below like gangbusters. Like it won’t stop. Filled up about a third of a five gallon bucket before I shut it down

 

Ok I’ll retry the procedure tomorrow or Monday when I have time, thanks guys. I did try it with the fuel caps off.

 

I tried it again and that pressure isn’t building anymore sure was strange