Leaking out of fuel pump emplacement

I dropped my tank today to inspect the top of it, sadly everything up there was ok. So to find the true source of my leaking gas a buddy and I went to the gas station and started filling. I laid underneath until the leak surfaced ($50 later X.X). It started at the point where this arrow is pointing around the circle. (I don't know what part is what in that setup).



I also noticed that if I put the gas pump (the one that puts it in the tank now) all the way in it will only give me gas in about .20c increments, as if the tank is full, but if I pull it out an inch or so it fills fine, though I don't know if it stops when the tank is full or not because as soon as the leak started I told my friend to stop pumping.

So do I replace whatever I need to around the pump or whatever that piece is called, or do I have something else amiss that would cause the gas pump to overpressure the seal thus causing the leak? (If thats possible). Thanks for all your help guys.

Untwist that lock ring, pull the sender assy out and replace the big o-ring. After cleaning any dirt or gunk out of the groove and off the sealing surface of the sender.

BTW, the o-rings do go bad after a while so I doubt there's an overpressure issue. Plus, it was leaking when you were just filling it so there couldn't have been any pressure then.

It did make it to full before the leak started though. Also could you link me to the part on Advanced? There the most local shop around here and I want to make sure I have the right part.

Thanks. Gonna try and do it my next day off, whenever that is. I'll post back if it solved it.