2003 ford taurus, when i fill my car with gas, the gas gauge does not go all the way to the full mark.

The sender in the tank could be going bad or getting hung some how. Could also be a loose connetion.

Sounds like a bad gas gauge. ;) I'm not a mechanic though. hehe However, I had gas gauge trouble with my Pontiac Aztek 2003 and I just ran the trip meter every time I filled up my car. For the Aztek, after about 300 miles I would need to start filling my car again and then reset the trip meter. You could use this as an option instead of trying to pay a bunch of money to fix the issue. You just have to know how many miles you can go on a full tank before you need to fill up again. Hope that helps.

hi gail both of your answers are correct,Inside the gas tank is your sending unit it is identical to the one in the toilet,there is a float that goes up when you fill it and down when empty,you are lucky to have it working the way it is the glass being half full!rather than it being on empty,I think the sender is not sold seperately,meaning the fuel pump comes with it and sold as a complete package,but call your part's store,Also fuel filter good time to change it,GOOD LUCK!