Water in fuel in my Freightliner M2, where is it coming from?

If it’s rain water getting in there and they are square tanks there is only two places to look. The fill cap or the fuel level gauge or gauge block-off plate on top of tank. The common standard little Freightliner caps that have the three or four 3/8 inch round dimples on the top of them are not air tight.

On my FL60 straight truck the rain water when parked would run straight down the front corners of the box body and flow onto the tank fill cap. I had to divert the water with something sometimes to keep it out of the open neck if I was fueling during a rain.

Newer M2’s use the same tanks and caps.

 

Then there’s the obvious... change fuel stops

 

I had this happen recently. It was the ####ty fuel I was getting from a local truck stop. Once I changed locations, it went away. You may be able to Google the place where you got fuel from and see if anyone else had the same problem.

 

Do you really have water in your fuel....??

My cummins is giving me the water on fuel light but I have no water in my fuel... I do have a bad sensor on the water separator

 

Ah. Are you sure it's water, and not coolant?

Monitor your radiator coolant level very closely. Coolant can get into your fuel in several ways, depending on what equipment you have. Some of those ways can mean an engine rebuild. Others might need much less serious work done. Replacing some fuel filter assemblies, for example.

 

Do you keep your tanks full? Condensation is bad this time of year especially in the south.

 

Check to see if your engine has a water drain on the bottom of the fuel filter assembly like on a DD15. Even if you change the filters on that engine, the water drain still has to be opened.