I have a fuel leak from a device on the driver side. I am not sure what the part is called, but is has two fuel lines and two I think coolent lines running to it. I think it is a fuel heater. The end that comes from the filter started to leak. When I was checking it, it seemed like the white plastic end is loose. Is there a o-ring in it, or can it be fixed or do I have to replace the whole thing?

What is the part called so I know what to ask/look for?
Thanks for any help.
87 300d

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1987 300D Turbo