FASS is a leader when it come to diesel fuel injection systems. FASS stands for Fuel Air Separation System and is a combination diesel fuel lift pump and fuel filtration system. These systems are designed to improve your truck’s fuel mileage, engine performance, and extend the life of your diesel injection system. Get the most out of your Ford Powerstroke, GM Duramax, or Dodge Ram diesel with a FASS Fuel System.