Very similar situation. Compared resistance on both old and new sending units. Full was about 9.5 ohms and empty was 76. Not too far off what was posted above. New one was purchased because old one was suspected as reason for gauge not working. Hmmmmm
Installed the new one and it does the same as the old one - with key on, the needle barely reaches the empty mark. Using the gauge checking methods posted earlier, found that grounding the gauge wire pegs the needle to full as described. Placed test light in line to terminal on sending unit. When key is turned on, tester lights up for about 3 seconds and goes out, and needle does not move on gauge.
What am I looking at here, a problem with the gauge, or maybe the voltage limiter? Although, the temp gauge appears to be functioning properly.