Have not tried anything yet but the fuel gauge on my 98 ford ranger always reads past full. Really don’t know where to start on this one either any help would be greatly appreciated.

 

1989 and up Ford fuel gauges use 16 ohms for Empty and 160 ohms as Full, so say 90 ohms for 1/2 tank

The Sender in the gas tank is connected to a Float, the sender is a Variable resistor, like a light dimmer or volume control, so it changes OHMS/resistance when rotated but the float

0 ohms is what a straight wire would read, no resistance to speak of
High or infinite ohms would be no connection

Since Gauge uses 160 ohms as full and it shows Full, or higher, then I would guess the wire to sender is broken or corroded badly so no connection
If wire was shorted to ground then you would see Empty, because it would be 0 ohms

Where to look?
The wire on the back of the dash cluster is a Yellow/white stripe and runs to the top of the gas tank , with 1 Splice for the Computer hook up, pin 12 on computer(PCM)
There is also an Anti-slosh module on the back of the cluster, which is a known issue on Fords, but usually these cause gauge to show Empty all the time, not full, usually

In any case you will need an OHM Meter to start testing