Fuel gauge, gas tank, or fuel pump ?

I have a 2001 Lincoln LS V-6 automatic. When you fill up with gas the gas hand will not go all the way up. When the low fuel light comes on and you fill up again, it will only hold about 14 gals. of gas. it has an 18 gal. tank. What could cause this. Thanks.

The LS has two fuel level senders, one in the left side of the tank, and one in the right. It sounds like one of these has probably failed.

Replacing one or both of them is not difficult. Both can be accessed without removing the fuel tank. (Remove the rear seat bottom, and there are two hatches to get to both sides of the fuel tank.)

Thanks. Is the fuel level sender attached to the fuel pump module or is it seperate ?

Thanks. Is the fuel level sender attached to the fuel pump module or is it seperate ?

Attached. There are actually two fuel pump modules, the main electric one and the jet pump one. Each one has an attached fuel level sender.