Help! Weeping fuel line

[roger brown]

I have a 1990 S2. The fuel line has a small black connector at the rear of the engine block. It joins the main feed from the fuel tank to the pipe running to the engine. The connector is weeping petrol. It might be a way one valve to stop fuel flowing back to the tank.My Ford dealer can't identify it on his parts diagram and David Gerald say they've never seen, heard of or fitted one.
I need to do some thing about. Can anybody help identify what it is, where to get a replacement, or otherwise what to do about it please? Thanks folks.