Water in Fuel? When Do You Drain the Filter?

If you get bad fuel you might get that warning. I bought my truck with 70K on the odometer and I've now put on 79K of my own. In nearly 5 years of ownership I've never had the WATER IN FUEL light come on. I've only ever touched the filters when I do my annual/15K mile oil change and fuel filter replacement.

Some cheap insurance would be to keep a 10x10 tarp under the back seat and a small plastic cup if you have to do this in an emergency situation. The rear filter is directly over the drive shaft and when you drain it the fuel hits the shaft and goes everywhere. If you place a small cup under it you can catch the fuel and avoid a mess.

Also, the front filter drains directly on top of the front axle. I attached a piece of 1/4" rubber hose to mine and routed it up by the radiator. This makes the outflow easier to see and also avoids a mess on your axle.

KJ

There are two water in fuel(WIF) sensors. One on both filter units. It is recommended to pullover as soon as possible when the light comes on, but keep in mind that both filters are water/fuel separators so even if the primary filter under the bed fills up with water, it will take some time(many miles) to fill up the secondary filter up by the engine.

The only time I had WIF sensor issues was when I accidentally twisted the wires when I performed a filter change. This exposed some of the wires causing the alarm to go off if I drove through a puddle of water and it splashed the exposed part of the wire harness. I changed the sensor/harness (about $35 online) and it never came on again in the past three or four years.

You should not have to worry about this light if you change your fuel filters at their recommended intervals. Again, keep in mind that both are water/fuel filter separators and even if one is full of water, it has to fill up the second one before it gets to your engine which takes a long time and many miles. This is likely not going to happen quickly unless you have a massive amount of water in your tank which is dang near impossible.

Periodically drain the filter(s), that too should be in the manual. I have never had the warning and never saw any evidence of water in the drained fuel. I drain into a clear bottle, let it set for a day or more and nothing. Having said that, I better pack a jumpsuit.

With the Ford 7.3 mostly I just add some diesel fuel supplement, found in a white can available at any truck stop. It adsorbs water and removes it from the fuel through normal combustion.