The fuel filter/water separator protects the fuel injection pump by removing water and contaminants from the fuel. The construction of the filter/separator allows fuel to pass through it, but helps prevent moisture (water) from doing so. Moisture collects at the bottom of the filter.Refer to the maintenance schedules in the owners manual for the recommended fuel filter replacement intervals.For draining of water from canister, refer to Fuel Filter/Water Separator Removal/Installation section.A Water-In-Fuel (WIF) sensor is attached to the bottom of fuel filter element.The fuel heater and fuel temperature sensor are installed into the side of the filter/separator housing.