First thing to establish is are you dealing with pipe threads or an inverted flare fitting.
Pipe threads require sealant, several options are available.
Inverted flare fittings do not require sealant.
This^^^^^
And use pipe dope on tapered pipe threads around fuel systems, not tape.
Because tape will wick fuel(turns yellow) and is hell if you ever remove the fitting because little pieces of teflon tape will be everywhere and hard to keep out of your fuel system.
And if you apply the tape wrong to begin with you will have tape in your fuel system from the get go. Avoid teflon tape around fuel systems is my advise.
