Going to haul the horses to a show and scrolling through menu and notice that the DEF says below 1/2 full. Roll into local ford delaership and buy 21/2 gallon jug and truck only takes 1 gallon?????? Service manager comes out and checks level in the dash and DEF says ok so it is good to go??????. My marth tells me this is a cab chassis and should have a 6 gallon tank so below half shoud have easily taken the 2 1/2 gallon. Truck pulled 16,000 pounds for 7 hours and def stills says ok any ideas???

 

no comments from anyone????????????????????

 

It's not an exact science, def tank and all....

 

I will put it this way, they got a mind of there own.lol

 

In the DEF tank, there are just 3 contact points that measure resistance relative to a 4th common contact at the bottom of the tank, and that resistance value changes when various points are submerged. It's not a calibrated tank level measuring device. I go through the system check screen periodically and refill whenever it says less than 1/2 full so I never have to run it down to empty... that's all it's for. It's not for telling you how many gallons/litres you should add to the tank.

You're saying your truck says everything is OK, and you've been driving it and it has been working so I feel that there isn't really a problem here... heck if the DEF level never dropped at all and everything still worked fine I'd be okay with that.

It's almost like the windshield washer fluid tank. It's not really a concern as to how full it was, as long as you stop adding to it when you see the fluid coming up the filler neck, and now it is full. I top that up periodically as well and I don't care what level it was at before or how many litres I was able to put into the tank. I top up DEF just like washer fluid so I don't get the big fuss about it. I kept the OEM filler hose which seals great and I never lose a drop of it anywhere.

 

FWIW - First, and only, time my message said less than half full I thought I would dump in 2.5 gallons and it only took 2.

 

Depending on your use, you have to run it for a bit with it reporting under half then an entire 2.5 jug will fit.

 

thanks for the replies. Maybe I don't have an issue but the 2 times i have filled the truck it said 800 miles to empty and only took 2 gallons and this time it was saying half empty and took only a gallon. Keep in mind this is a cab chassis that has a 6 gallon def tank. Worries me a bit as I travel long trips loaded with horses and it is usually in isolated areas and at night

 

Sensors maybe wired in the wrong order. Have your dealer check it.

 

As a cab & chassis model, I would suspect that there is an issue with how the DEF fill hose is routed with your body. It sounds like you have have an issue with the fill tube getting air bound and not allowing you to fully fill the tank.

As was stated earlier, they do seem to have a mind of their own. Mine is not all that consistent either. I usually run it down to about 200 miles to empty, dump 1 full jug in then drive another 500 miles before dumping the second jug in. Sometimes it takes it all, sometimes it doesn't. The miles to empty is simply a guess since the truck has no way to actually monitor how much DEF is used and driving & atmospheric conditions differ constantly affecting your usage rate.