fuel leakage

[carlo venturi]

Dear friends,
has anyone faced some fuel tank leakage from 815 models? I discovered, from years to date, my 1.8 coupè having it from the threaded collar joining the long iron filler to the threaded brass trunk welded to the fuel tank. I begin to believe that convoluted iron filler culprit of that leakage because I found it not firm in his position (it has no screw\bolt fixing it to the body). I made many attempts to solve the question (changing sealer, removing tank, etc). Is it only a question of torquing that castellated collar to hold in position that long filler? And how can the trunk welding resist against the torque? Tell me also, if anyone checked his fuel tank at a professional shop. Regards, Carlo.

P.S. Flavia 815. spare parts manual, does not state any improvement during fuel filler construction.