Gauge
Doc here,
imp:
On the Instrument Cluster, You should have on the reverse side of the Gas gauge, If It's Stock, a laminate card with three terminals marked "S", "G", and "I"....
While you want to inspect all three, for Corrosion, or loose or burned connections or laminate card Trace opens, the "G" is the ground and pay extra attention to that..The "S" is sender, and the "I" is 12 volt switched Ignition..Check also the cluster plug for corrosion, or ill fitting pins.
While you have the cluster plug out, Using an ohm meter to the sender wire going to the tank, with The sender at the tank unhooked, you SHOULD read infinite readings at R x 1 scale or auto range on the meter to ground, If you show any readings at all, you need to inspect that wire for shorting or chafing..
To include or exclude the sender as a suspect, get a couple of 1/2 watt resistors from radio shack, 10 to 15 ohm, 50 ohm, 150 ohm, hook up the cluster and apply power with The sender hooked up...
what does it read? Full or Empty?
Unhook the sender, It should peg the opposite way..
then using alligator clips, jump your resistors from the sender line to ground..one at a time..
depending on the actual resistance value of your circuit, you should get (on at least one resistor) a half tank reading..or ANYTHING besides pegged full or empty..If that happens on ANY one of the resistors, your Circuit and Gauge are Both Good, replace the sender..
If it doesn't happen, and the wire , cluster connections and terminals have all checked good, Replace the gauge..The Wheatstone bridge inside the gauge has been damaged and beyond the range of resistance provided by the sender..or may just be flat open.
The Tank SHOULD ALWAYS have a ground wire on it..There should be a ground tap somewhere in the area of the sender/Fuel pickup bezel, and that wire should go to a hard frame ground..The tank sits on rubber mounts...and depending on aftermarket add~ons may or may not have rubber hose on the fuel lines, isolating the tank from hard ground.
Doc
imp: