Yes and no. You can test it, that isn't a problem, but I don't know what the voltage levels are that you would be looking for at a given point. I'm also not sure how linear the gauges are.
Basically, you have a variable resistor (AKA Potentiometer) called the fuel gauge sender connected to the arm in the tank. As the arm moves it changes the resistance of the pot which changes the voltage output. You can assume 0 volts is empty because the needle drops that way when the power is off.
The Sender is grounded at one end and connected to the gauge at the other. the voltages are supplied in the gauge itself. if the problem is purely electrical, somewhere you have too much resistance. The most common cause of unwanted resistance is corrosion. Either the contacts at the gauge, the contacts at the sender or in the potentiometer.
The only way I know of to test the Gauge would be to have a collection of Potentiometers of a know value, ground one end to the chassis and connect the middle connector to the S on the gauge after removing the sender from the circuit. with the gauge powered you should see the needle move. Adjust it to Empty on the gauge, remove the pot and measure the resistence (ohms) across those two points. reconnect, adjust to full, disconnect and measure. this will get your minimum and maximum values for the sender. if it doesn't reach empty or full you need a higher value test pot.
Once you have the min and max you start working down the circuit (unpowered) and see where the resistance changes. Easy in the dash, hard at the tank.
If you replaced the gauges with after market gauges, they MAY have an adjustment. I think the originals do but it is on the rear of the gauge and covered usually.
There are two ways to do an adjustment to where you think the level should be. one, is hit or miss. turn the adjustment screw. hook it back up, see where it is and repeat till you get it right or give up and get it good enough. you can do this with the tank full, you are just going to move the needle back from overfull until it is just on F. Though it still might not be perfect.
The second way, is to get your tank to empty, measure the resistance from the sender. Set up a small power supply to the gauge At I (+) and G (-, ground) on a bench. Adjust your variable pot to the same value as the sender and connect it between the S on the gauge and the - ground on the power supply. Adjust the adjustment screw until the needle sits at E. I would adjust the pot now and make sure the needle moves toward full.
Hit or miss might be just as easy, or easier than emptying the tank.