Could be something as simple as a bad connection or gauge or it could be the sending unit. If you want to tackle this yourself, the sending unit is about $80.00. A gauge from a junk yard, if they;ll sell you just the gauge about 25.00. If its a bad connection, well what ever your time is worth.
If you want to try testing the system yourself, stop by radio shack and buy a 50, 150, and a 300 ohm ¼ watt resistors (about $2.00). Pull the connector next to the tank. Turn the ignition to run, and find the Yellow with White stripe wire and insert in turn each resistor between the Yellow with White stripe wire and ground while watching the fuel gauge. If the gauge reads between near empty and full, the gauge and associated wiring are working properly. If not, you’ll need to check the wiring between the tank and the gauge and or the gauge itself.
Next, using a voltmeter set to ohms, back probe the Black with Orange stripe wire to ground. If you read less than .2 ohms the ground circuit is good. If not, you’ll need to find the open circuit and or repair the bad ground point.
If both tests indicate the gauge is working properly and the ground point is good, you’ll need to replace the sending unit.
2001 Ranger Edge 3.0 V6, 5 speed M/T
Limited Slip Differential, James Duff Traction Bars
Kumho 30x9.50 15 MT / Black 297 Series 15x7 Rims