need help with 73 Charger fuel gauge.

[Street Fighter]

I have a 73 Dodge charger that have a fuel gauge problem.I replaced the gauge in the tank because it was giving the wrong reading.At the half way mark it was really out of gas.If you abbed as little as 3gals. to the tank it goes to full.The new gauge does the same thing.Took the frist one back because I felt that it was bad, I believe that It's something else. It's getting a good ground. I tried a tank unit made for something else connected the wires and worked the level by hand and the gauge shows correct, if I moved the level to full it showed full, halfway showed half full, what is wrong? Could both of the new tank units I bought be bad? I got both from the same store.

[bills98ta]

If it works out of the tank, maybe the float arm needs bent upwards. Sounds like it's hitting the bottom and lifting itself...

[Street Fighter]

If it works out of the tank, maybe the float arm needs bent upwards. Sounds like it's hitting the bottom and lifting itself...

The unit I used to test the reading of the inside dash gauge was one that fits a different kind of car. I worked it by hand,not the one in the tank. The one in the tank is the one that is not working. and it's not bent,remember this is the second one I have bought besides the one that I frist removed from the tank because it did the same as the other two I have bought. So it's three that did the same thing.

[79Firebird_99TA]

The unit I used to test the reading of the inside dash gauge was one that fits a different kind of car. I worked it by hand,not the one in the tank. The one in the tank is the one that is not working. and it's not bent,remember this is the second one I have bought besides the one that I frist removed from the tank because it did the same as the other two I have bought. So it's three that did the same thing.

Sounds to me like some additional resistance in the circuit. Where is the fuel guage when empty? The reason why I ask is, my `79 Firebird has 50 extra ohms of resistant in the circuit and will run out of gas when the gauge shows around 3/8 tank. The spec for my car is 0-90 ohms (sending unit). I measure 50-140 ohms. When it's full of gas, the gauge sits at 3 o clock.

I'm just wondering what range you have on the gauge itself if moving sending unit back and forth.