Take the float off and immerse it in very hot water. If it blows bubbles, there's a hole (very common).
After that, follow this flow chart:
Key on, W or W/B wire disconnected at ignition coil
- at the tank, disconnect the sending unit wire and touch to a known good ground.
Does the gauge needle go all the way up?
If yes, go A. If no, go to B.
A:
- now touch the sending unit wire to the sending unit ground wire.
Does the gauge needle go all the way up?
If yes, remove the sending unit and hook up its wires. Lift the float all the way up.
Does the gauge needle go all the way up? Then you have a float issue or you accidentally fixed a bad connection.
No? Sending unit open, poor connection between resistor and moving contact.
B:
Go to the gauge and ground the where the sending unit wire hooks up.
Gauge goes all the way up? Corroded connectors, connections, frayed sending unit wire.
Gauge reads low. Test the voltage at the gauge power wire. Roughly 10v or a pulsed 12v signal? Gauge needs replacing or recalibration. Low voltage? Replace the instrument voltage regulator. Clean connectors and green fuse cionnections. Check the gauge ground at the same time.
Gauge calibration procedure to get a working gauge but not necessarily 100% accurate. Leave the sending unit out but hooked up. Jimmy the float arm so it is all the way up. Remove the two circular stickers to expose the adjustment slots. Key off, tweak one adjustment or the other unit it just reads full when the key is turned on (do not make adjustments when the gauge is powered). Lower the float and make sure it goes to empty. Tweak the adjustments until you get both a proper full reading and a proper empty reading. Should be OK now.
John
