Fuel Gauge Trouble Shooting Help Needed!!
If neither gauge works it could be several things, including but not limited to
the connector to the cluster
corrosion/ loose connections right at the gauge studs
bad / poor gauge regulator, or bad connections in the socket it fits
(DO you have a rally cluster?)
Of course the gauges themselves
And of course sender wire problems. Don't forget the temp sender wire goes through the bulkhead connector, which could be a bad connection.