You probably have a 29 gallon tank
, but the problem is that they don't vent very well so it appears to be full, when they are not. Thus you get about 23-25 gallons before the pump clicks off and says full. Try this (if you have the time).
Once the pump clicks off, see if how long you can trickle fuel in. If you sit there for 10 minutes with the foam rising and falling down the filler tube, yet never seems to get full, then you know you have a vent problem. You should be able to fill the tank
most the way up the filler tube with no problems.
The vent problem is a design issue from Ford. You can do what is called "harpooning" your tank
, which is basically dropping your tank
, getting inside your tank
and cutting the vent tube. This will allow your tank
to fill quicker and fully to its capactity.
And yes, your computer readout will be wrong most the time...