Another fuel gauge reading thread

[Walter Moore]

I know that this has been beat to death, but back when I put my car together I replaced the fuel tank sending unit with a new one, and like everyone else the gauge read 3/4 full with fuel all the way up the filler neck. I was replacing my electric fuel pump this weekend, and drained the tank so that I could replace all of the hoses. This gave me an opportunity to pull the sending unit back out and "tweak" it a little.

 

I started by bending the arm slightly, to get the Empty reading a little higher.

 

Then I noticed something strange about the position of the rheostat when the arm was in the Full position (See the picture Rheostat_1)

With the arm on the travel limit, the wiper of the rheostat was not at the full travel of the wire wound resistor. Measuring it with an Ohmmeter the reading for Full was 14 Ohms, and empty was 85 Ohms. (Which was full electrical travel.) By bending the travel limit slightly as shown in the picture SendingUnitTravelLimit, I was able to get the wiper all the way to the end of the rheostat. In that position the resistance reading is around 4 Ohms. (Note that I have drawn a rectangle around the Full travel limit for clarity.)

 

When I put everything back together, the gauge now reads E when there is no gas in the tank, and slightly above F when the fuel level is all the way up the filler neck. It isn't very linear in between, but given the shape of the tank, I wouldn't expect that.