The fuel filter on a 1999 Dodge Dakota with the 5.2L V8 engine is located
on the frame rail, near the fuel tank, on the passenger side of the vehicle. It's usually close to the rear axle. You'll likely need to get under the truck to access it. It's a cylindrical filter.
Keep in mind that precise location can vary slightly depending on specific options and trim level. If you're having trouble finding it, a visual inspection from underneath, referencing a repair manual or online photos specific to your year and model, is recommended.
