fuel gauge does not read correctly

[culp71]

trying to dial in and work out the last few bugs on my restored 71 cuda.
the fuel gauge doesn't read correctly.
I had replaced every part and thought it was working correctly until I filled the tank for the first time  a couple days ago.
when the tank is full the gauge only reads about 1/2 tank or slightly under, so when gauge is close to E I still have close to half tank left. any insight on what is not correct. thanks

[318Stroker]

Did you use an aftemarket repop sending unit? If so, they are all calibrated wrong and they are junk.

[DeathProofCuda]

You can sometimes bend the stops for the sending unit float arm to get more or less swing of the arm.  This changes the resistance of the unit and may help to get the correct empty and full resistance readings.  With the sender out of the tank and connected to a good ground, you can bench test the sender to verify that your gauge is reading correctly before installing it in the tank.

[blown motor]

I have the same thing on my 74 Challenger. When I fill it the gauge shows 3/4. I set the trip meter when I fill it and I'm good for 200 miles but it would be nice to have it working correctly.

[headejm]

You can sometimes bend the stops for the sending unit float arm to get more or less swing of the arm.  This changes the resistance of the unit and may help to get the correct empty and full resistance readings.  With the sender out of the tank and connected to a good ground, you can bench test the sender to verify that your gauge is reading correctly before installing it in the tank.

You definitely want to bench test a new sending unit. Super easy to do. Watch Cody's video in our Resources section.

[anlauto]

They're never accurate 

[culp71]

ok, great 
I checked my info and looks like I bought the "Right Stuff" Detailing Fuel Tank Sending Units ESU7001 from summit racing...
https://www.summitracing.com/parts/RSD-ESU7001

so pull from tank and simply bend the float arm....or does some one offer one that is correct as I would think by bending the arm it may not have the correct throw to read correctly at both E and F

[culp71]

what is the proper ohms reading for E and F?
maybe easier to put a electrical in line resistor to alter signal to gauge,
as I remember dropping the tank was not simple or quick, and the wire is a lot easier to get to...

[shawge]

Miller C-3826 gauge checking tool has the following level to Ohms:

L  = 73.7 Ohms
M = 23.0 Ohms
H = 10.2 Ohms

[YellowThumper]

It would be soooo much easier if they read too full instead of not full enough.
Then all it would take would be a simple in line resistor.

[Joegrapes]

Common problem. None of the aftermarket sending units will work. I know I've tried them all over the years trying to get my gauge to read correctly. I've tried bending the arm also. You can get it to read better one way but worse the other. I finally gave up and found a NOS unit. It was not cheap but my gauge works perfectly now. I my opinion it was money well spent. I just couldn't get over spending so much time and money getting these cars to look and run great and then having to put up with something as little as a fuel gauge not work right.

[DeathProofCuda]

ok, great 
I checked my info and looks like I bought the "Right Stuff" Detailing Fuel Tank Sending Units ESU7001 from summit racing...
https://www.summitracing.com/parts/RSD-ESU7001

so pull from tank and simply bend the float arm....or does some one offer one that is correct as I would think by bending the arm it may not have the correct throw to read correctly at both E and F

Negative...you don't bend the float arm. You bend the stops for the float arm.  This allows the float arm to have a longer (or shorter, depending on what is needed) resistance range.

[Scooter]

I watch these treads with interest when they pop up. When I fill my Challenger the gauge shows full.. then drops to 1/2 tank after using just a couple of gallons. Buying NOS seems to be no guarantee for accuracy from what I've read. 

[340Challman]

Common problem. None of the aftermarket sending units will work. I know I've tried them all over the years trying to get my gauge to read correctly. I've tried bending the arm also. You can get it to read better one way but worse the other. I finally gave up and found a NOS unit. It was not cheap but my gauge works perfectly now. I my opinion it was money well spent. I just couldn't get over spending so much time and money getting these cars to look and run great and then having to put up with something as little as a fuel gauge not work right.

This is disturbing to find out. I'm starting my resto and would really prefer my gauge to be accurate when I'm done. I have been doing the trip meter trick as well. I wonder if one could buy an after market one and then measure the resistance through the range of motion and then provide the values to the guys doing the calibration of our instruments to get accurate indication. Of course you would need to know the exact travel limits of the float when in the tank. Thoughts?

[HP2]

Not sure what years tank access is like, but I can access the sending unit out of my 74 by simply removing the driver side rear tire. No need to drop the whole tank.