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In order to run, your engine needs both air and fuel (either gasoline or diesel). Water can cause severe damage if it contaminates gasoline or diesel. While there’s no way to completely eliminate all traces of water from the fuel, the situation can be monitored, which is the purpose of the water-in-fuel sensor. The water-in-fuel sensor is typically located in the fuel filter housing, and constantly checks the electrical conductivity of the diesel fuel in the filter as the two substances have different conductive properties. If there is excessive water found in the fuel, the sensor sends a signal to the vehicle’s instrument cluster to illuminate the water-in-fuel warning. If the water-in-fuel sensor is not working properly, you may not be able to tell if your fuel quality is proper. Excess water in your fuel can cause a rough run, excessive white exhaust (water vapor), and a stalled engine.
There is no set maintenance interval for most water-in-fuel sensors, though if your owner’s manual says to replace it when the fuel filter is changed, do so. Have one of our expert mechanics diagnose and replace the water-in-fuel sensor if required.
The sensor itself is not critical to replace in a timely fashion, though it does indicate whether or not your fuel quality is adequate. You will not be able to tell if you have a fuel issue otherwise, so replace a faulty water-in-fuel sensor as soon as you are able to.