How do I determine the ohms of my current fuel sender?

If you're not sure of the fuel tanks impedance, determine it's' resistance by following this method:

Disconnect the fuel tank sender from the gauge.

Connect an ohmmeter across the fuel tank sender. Connect the meters positive lead on the fuel tank sender's output and the connect the ground lead to the fuel tank sender's flange.

Manipulate the position of the float arm with a piece of wire or some other device so that you can position the float arm in the full and empty locations.

The range for Stewart Warner fuel senders are: Empty - 220 to 260 ohms; 1/2 tank - 80 to 120 ohms; full tank - 20 to 50 ohms. This is normally noted as 240 ohms at empty and 33 ohms at full.

GMAC fuel tank sender will read in the opposite direction. At empty, it will read zero ohms and at full it will read 90 ohms.

Ford/Chrysler fuel tank sender will read zero ohms at empty and 73 ohms at full.