by v8astregt » Tue Aug 10, 2010 7:17 pm
Do you have a digital multimeter? If so, great, if not, you can get one for like $15. When you have it, turn the dial to the resistance setting, or the Ohm scale (looks like a horseshoe).
It's pretty simple. Take one probe, and stick it in the terminal of the wire that leads to the fuel sender. There should 3 wires, one fuel sender wire, one for the fuel pump, and I think there's a 3rd ground wire. Trace the wires to see which one connects to the fuel sender potentiometer, which is attached to the float rod. Pretty easy to spot. Anyways, connect one end of the multimeter to that wire, and connect the other to the body of the fuel sender, essentially the ground. Make sure you sand off a nice spot of bare metal to get a good connection.
Once you have those two connected, move the float arm through it's entire swing. A proper unit will have a reading that varies linearly from one extreme to the other. I'm 95% sure this GM sender has a range from 0-90 ohms. My guess is going to be that it will be bad, and show infinite resistance. Then it's time for a rebuild!
Not too hard to do!
75 Pontiac Astre GT: 406SBC/TH350, roll bar, S10 goodies, down to 11.47 so far, more to come later.