The water-in-fuel (WIF) sensor warns you when water has collected in the fuel filter or separator, protecting the expensive injection system from corrosion.
What it does
Diesel fuel can carry water, which corrodes and damages injection components. The WIF sensor sits in the fuel filter or water separator and lights a dash warning when water reaches a threshold, prompting you to drain it.
Signs it is failing
- A water-in-fuel warning light
- Water present when you drain the separator
- Rough running or hard starting from water in fuel
- A stuck-on or non-functioning warning
Replacement and what to know
If the sensor itself fails, it is replaced; more often the warning is real and the separator simply needs draining. Never ignore a genuine water warning, since water in the fuel damages the pump and injectors.
Frequently asked questions
What does the water-in-fuel sensor do?
It warns you when water has collected in the fuel filter or separator so you can drain it before it reaches the injection system.
Should I ignore the light?
Never ignore a genuine warning. Drain the separator promptly, since water corrodes the pump and injectors.
Can the sensor fail?
Yes. If it reads incorrectly it can be replaced, but confirm there is no actual water first.
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