1980 ford 350 fuel gauge does not work where to start, tank or gauge? on 1990 Ford F-350

Problem is fuel gauge has not worked for a long time, has fuel in tank 7 or 8 gals. Where to start looking for trouble tank or gauge?

Asked by for the 1990 Ford F-350
Typically, we see more issues with the tank sending unit than any other problem. A resistance test with a volt/ ohm meter is the only way to diagnose it accurately. I suggest this site on the details: