12v or 6v electrical system?
original tank sender (adapted to work in your tank) or later 12v Suburu sender?
If 12v system and Suburu sender and original 6v gauge, you might have a gauge-voltage problem (a runtz-style resister is recommended by many people), and the ohms-rating of the sender does not match the that needed/expected by the gauge (as posted by 5wests).
