I have been having issues with my fuel gauge since the day I brought the car. I made up a tester and checked wiring and gauge response. The gauge sweeps from empty, 1/2 and full no problem using my tester so no issues with any of that. The sending unit must be the cause. The main issue is that when full, the gauge reads 3/4 and when the tank is just under 1/2, it reads empty. I was hoping that the float was leaking and partially sinking in the fuel.
So today I pulled out my fuel sending unit. I am happy to say that I have an original lock nut in place because the new repro ones are notoriously thin and can cause leaks. The bad news is, somebody in its life has changed out the factory sending unit for a new Chinese repop. And of course you guessed it, it's junk.
The range is 10.0 Ohms- 77.5 Ohms. On face value, you would think that's not too bad. But, two things are not good. One, the slider must have very light pressure applied to the rheostat because sometimes it loses resistance altogether. Second, the sending unit is vastly different to OE. I know the OE version is non linear and the repops are made linear. I wouldn't call mine strictly linear, but it is also very different to what it should be.
I read in
@dadsbee Superbird cleanup thread that he has the following readings from his OE sender compared to mine
Wayne's OE Jason's Repro
Full = 10.8 ohms Full = 10.0 Ohms
Empty = 69.6 ohms Empty = 77.5 Ohms
1/2 tank = 26.8 ohms 1/2 = 41.3 Ohms
3/4 = 19.1 ohms. 3/4 = 25.5 Ohms
1/4 = 41.2 ohms. 1/4 = 56.3 Ohms
The other thing I noticed is that the the bend in the arm was far more pronounced on mine than the OE version. In a vain effort to improve the readings, I straightened it out a bit, but don't know at this stage how much difference it will make.
So, for now I have put the sender back in and will fill the car with gas tomorrow to see if there is any difference. I replaced the seal with one I got from DMT.
I am now looking for a good used one (Part number 3420 848) or NOS if it's possible to find one. My car is a 383 4bbl.