Fuel Gauge

You have your volts and ohms terminology a bit backwards. You read voltage with a voltmeter and resistance (in ohms) with an ohmmeter.

The sending unit inside the gas tank is simply a variable resistor with one end tied to ground and the other being the wiper which moves up and down. To test it properly take it out of the tank and put it on your bench. Next use your ohmmeter, not your voltmeter, and touch the 2 leads together to prove the meter is working. The meter should show close to zero ohms. Next attach the ground (black) lead to ground on the sensor and the other red lead to the output terminal. Now read the meter and it should vary as you move the float up and down. If it does not your sensor is bad (which is likely). Sometimes you can gently bend the wiper arm to make better contact to the resistor and fix it but most likely you'll have to replace it.

When you put the sensor back into the tank be sure to use the ground strap and install it properly so that the sensor gets a good ground. Good Luck.