Fuel Gauge Issue

What I did was drain out all the fuel

Then add back one gallon at a time and take ohm readings.

Keep in mind that there is so e additional resistance in the wire from the sender to the gauge. So to get the best readings measure at the wire closest to the gauge.

The inner kick panel on the drivers side has a connector you can disconnect and measure there.

Lastly 1/2 the senders range will not represent 9 gallons in an 18 gallon tank. (tank shape)