Otto.
Do these steps
Power on
Disconnect sending wire at sending unit
Gauge Should go to full on gauge and beyond.
Put wire on metal should go to empty
Test with ohm meter from sending post to ground. It should have some resistance if it’s zero something is grounding the sending wire at sending unit side
Watch this. Substitute 30 for 90 ohms when listening
Fuel Gauge & Sending Unit Troubleshooting
