I didn't calibrate mine and it works fine. Although I suppose you could see how it works with your gauge in the high and low positions and bend the arm to get it where you want it. I doubt you'd need to.
Take a look there.. about halfway down the page refers to the fuel gauge.. good luck.
If the resistance falls in this ballpark (depending on how much gas you have in the tank), then the sending unit is fine. If it shows infinitely HIGH resistance, then the sending unit could be bad OR the wire from the tank to the gauge could be open.
1986 Jeep CJ7 (photos)
Remanufactured 258, ARB lockers front & rear, 4.10 Yukon gears, 35x12.5" Super Swamper SSR's, Motorcraft 2100, 4.5" Rubicon Express Extreme-Duty lift, York 210 OBA, Big Daddy steering, Tatton rear CV driveshaft, Herculined interior, TJ flares, lots of body & upholstery work
If it is reading full all of the time then it is going to ground. If it reads empty then you don't have a ground. If you want to check your gauge take the red wire with the plug on the end of it off of the sending unit, take a piece of wire as a jumper, and run it to a ground (frame). The gauge should go to full. Don't hold it directly to ground for too long or you risk ruining the fuel gauge.