Do a search..
Hello Sputnick, there are a lot of threads on this subject, do a search for 'fuel tank sender' and you will find a wealth of info.
The search feature is located in the pull down menu under the 'Discussion Forums' tab
The fuel senders are notorious for not being accurate. The sender can be changed by either dropping the fuel tank, or lifting the bed to access the top of the tank. There ilso a post about how to repair the sender.
Hope this helps, Greg L