On a 1997 Ford F250 7.3L Powerstroke, the water fuel separator (also known as a water separator filter) is
located on the frame rail, near the fuel tank. It's typically on the
passenger side (right side) of the truck. You'll be looking for a cylindrical canister with fuel lines connected to it. It might have a drain valve at the bottom.
However, it's highly recommended you visually confirm its location. Use your owner's manual or a repair manual specific to your year and model if possible. A quick online image search for "1997 Ford F250 7.3L Powerstroke fuel filter location" might also help you pinpoint it visually.
