1998 v70 gas gauge reading about 3 gallons under?

JoebobNLacey · Post by **JoebobNLacey** » 30 Jun 2026, 20:35

New problem started about two months ago: gas gauge suddenly starts reading about 3 gallons under. Last 3 tanks I've filled it and gauge will only go up to about 15 gallons. Seems to read linear all the way down, haven't drained it to the point of turning on the light.

Did not do any work on the car when the problem started. What could have caused this?

gdog · Post by **gdog** » 30 Jun 2026, 23:09

Usually that issue is caused by a bad fuel tank sending unit in the tank. Kind of a PITA to get at but not terribly tough. Found this utube that may be helpful:

Haven't looked at the schematic but typically the sending unit is just a variable rheostat (effectively a variable resistor) so once you get access to the two sending unit wires, try unplugging them; gauge should go to full, or empty. Then short the wires and then it should go to the opposite reading.

If it's still reading low during above test, could be something with the gauge itself.

Post by **scot850** » 01 Jul 2026, 10:17

If you typically refill the tank and don't run it full to empty, then over the years the gauge has a contact area that wears more in the range where you run your tank levels. I don't recommend running tanks lower than 1/4 tank, especially in the summer as the fuel helps cool the pump which helps more when they get older. If you have not replaced it, in fairness the youngest P80 is 22 years old (C70) or 26 years old (the rest of P80's).

Neil.