I bought a 94 dodge 3500 12v diesel a couple of weeks ago, and the water in fuel light was on. I replaced the filter and cleaned the sensor, and the light went off. Now the light has come back on. Should I take the tank off and clean everything and replace the sensor? I think the sensor is working correctly.

 

How long was the truck setting up? You might have some condensation build up in the tank and lines. Pulling the tank is a good job, I would place a catch can (glass) under the fuel filter and drain into it. Let it set a few minutes and see just how much water if any is in the filter/seperator.

 

I bought the truck from a dealer, so I don't know how long it set up. I do know that it was used on a farm as an extra truck so it could have been sitting for a while.

 

Was the engine or truck washed ? It may be just water in the sensor itself. Mine would come on everytime i went through the car wash.Pulled the sensor off and smeared some silicone all around were the wires went into the sensor, no more lite.
If not then yes collect anything you drain out and see if there is water coming out with the fuel. If so definately drop the tank and clean it out and run a n additive that removes water.

 

Start running some fuel conditioners right away. They may suspend it enough to get it through. Keep the tank full as possible to dilute the water.

 

When I bought the truck it was on empty and the light was on. The next day I changed the filter and filled up. The light stayed on about two days then went off. My son ran it to about a 1/4 of a tank then it came back on, so I guess I need to drop the tank and clean it.