There is 2 Hoses that come out of the Bottom of the Fuel Tanks. And, Yes the Tank need to be drained to change any of the Bottom Hoses.

If the Set Up is stock the Hose coming out of the Tank is attached to a Big 46MM Nut (The Fuel Tank Screen is attached to the Nut). It has a Brass crimped on Collar on one end and plain Hose and a clamp on the other end.
If you grind through or file through the Collar and pry the Collar off it exposes a regular Hose Barb.
Once the Hose Barb is available you can simply buy for 5/16 inside diameter Fuel Hose and a Clamp from any Auto Part Store; that Hose is rated for Diesel.

The other Hose at the Bottom can also be replaced with 5/1`6" ID Hose and is the Fuel Return Hose.

However, I had a Fuel leak and it turned out to be the Steel Tubing had rusted through. So a good inspection in order.

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84 300D, 82 Volvo 244Gl Diesel