Bought my ranger a couple weeks back and theres an issue with the fuel gauge, when i start it the hand jumps past full then while im driving it will slowly go down to empty. any idea on what could be causing this?

 

Welcome to the forum

Depends on the year of the Ranger

But on most years 2003 and earlier, there is an Anti-slosh module on the back of the instrument cluster, when it fails you can get what you describe
If the sender/float in the tank was bad it would usually just stay on empty all the time