fuel leak need help fpr return

[melmount]

I did the shim 2 days ago. runs great,
I am leaking fuel i believe it to be where the return line threads on. That wide factory reusable gasket. Its a bit beat up.
Is it supposedto fit into the little aluminum housing along with the steel line? it wont. maybe to swollen? It may not be supposed to fit in. It may be a compression type of sorts. my biggest thing is it swollen and that the reason it wont fit in there? I can insert the tube then start the threads. The rubber goes into the female end with the trhreads but will remain outside the aluminum thingy? I am asking, i guess does it slide into both sides?
thx

[melmount]

turns out it was the drain valve O rings.ibought the 3of em last week.
The previous owner must ofrealized the rings leaked. Someoneput apieceof rubber between the valve and the housing. It kept it from leaking but I could not drain fluid to change the filter. I, at this point got the fuel out changed filter and ordered o rings from Replacement O-rings for Diesel Engines Recently i opened the valve with the key on to run the pump to clean the drain hose. I did not know about the rig job. been leaking since i used pressure to clean the hose. New O rings and fixed.