Water-in-fuel Sensor

Water is heavier than diesel and settles at the bottom of the filter. A warning light shows on the dashboard. Many filters have a drain screw. Fuel from poor-quality sources, condensation in partly empty tanks and wet filler areas are common sources of water. Keeping the tank fuller in humid conditions helps.

Water conducts electricity better than diesel, so the sensor detects it.

Water damages high-pressure pumps and injectors. Drain as instructed and replace the filter at intervals.