Fuel Sending Unit and Fuel Gauge

[303 Mopar]

I'm having issues with my fuel sending unit and fuel gauge to read anything close to correct levels and am hoping for your help.  I have tested multiple new sending units and all have the same result.

While the sending unit is outside the tank but connected and has a good ground, I can move the indicator arm and the gauge registers correctly.

As soon as I place the sending unit in the tank the fuel gauge only reads below Empty and does not move no matter how much fuel is in the tank. It is not the float because these are new units with new floats.  I have also grounded the unit with a lead to the negative terminal of the battery and still no reading.

Any help is greatly appreciated as it is driving me nuts!   

[Cuda Cody]

When it's outside the tank how many volts are you using to test it?  If you have a good ground and you know the sending unit and gauge are good then could it be a volt issue?  have you changed or modified the wiring in a way that the gauge might not be getting the full volts it needs to work?

[fc7cuda]

  I have also grounded the unit with a lead to the negative terminal of the battery and still no reading.

Normally the sending unit is grounded to the metal fuel line after the small rubber hose connection back at the tank.  Curious why your running a ground all the way up to the battery?  Did you confirm the sending unit is grounded.

[7212Mopar]

I am experiencing the same problem. I am on my second sender now. If I ground the wire, gauge reads full. Hook up to sender and gauge reads below empty or right at empty. No change if I attach a ground wire to the sender body in addition to the ground strap. The tank is at least 3/4 full if not 100%. The only change I made was changing out the gauge cluster regulator to the electronic ones. Look forward to reading more from this thread.

[Slotts]

I'm having issues with my fuel sending unit and fuel gauge to read anything close to correct levels and am hoping for your help.  I have tested multiple new sending units and all have the same result.

While the sending unit is outside the tank but connected and has a good ground, I can move the indicator arm and the gauge registers correctly.

As soon as I place the sending unit in the tank the fuel gauge only reads below Empty and does not move no matter how much fuel is in the tank. It is not the float because these are new units with new floats.  I have also grounded the unit with a lead to the negative terminal of the battery and still no reading.

Any help is greatly appreciated as it is driving me nuts!   

Let's review what we know and what we (me) don't know.

From what you have described, the fuel sending unit "outside" of the fuel tank will run the dash gauge from E to F with the full travel of the sending arm back and forth reading correctly, right? You mentioned the ground wire is a straight run from the - battery terminal. Are you using the fuel sending wiring from your installed rear harness or making another straight run to the fuel gauge?

If you are using the rear harness fuel sending plug connected to sending unit, I would ask another question of if your tank is original or has been replaced with a repop. My asking about that is with the sending unit working outside and not inside, if all of the wiring is the same, I am questioning if the arm on the sending unit is moving at all?

I would want to know if the float arm, once installed is catching on something preventing it from moving. We are talking about the same supplier of repopped  sending units, right? 

You could try tying a soft wire, like a 20 gauge length of craft wire, or something like that, wrapped around the float. Only put the sending unit, with this wire, into the tank and only hold it in place and then pull on the wire to feel if the arm is moving or possibly catching on something. Let us know what you find if you care to try this experiment.

Hope this helps.

Jim

[303 Mopar]

Hope this helps.

Jim

Thanks Jim.
From what you have described, the fuel sending unit "outside" of the fuel tank will run the dash gauge from E to F with the full travel of the sending arm back and forth reading correctly, right? - Correct

You mentioned the ground wire is a straight run from the - battery terminal. Are you using the fuel sending wiring from your installed rear harness or making another straight run to the fuel gauge? - yes, connected to the wire in the harness the entire time. I grounded the unit outside and inside the tank. @fc7cuda I added a ground to the battery while inside the tank and still no reading, so it is not a ground issue with the sender.

If you are using the rear harness fuel sending plug connected to sending unit, I would ask another question of if your tank is original or has been replaced with a repop. My asking about that is with the sending unit working outside and not inside, if all of the wiring is the same, I am questioning if the arm on the sending unit is moving at all?  - Its a repop tank from Dave, but the float is raising the arm since there is fuel in the tank.

I would want to know if the float arm, once installed is catching on something preventing it from moving. We are talking about the same supplier of repopped  sending units, right?   - correct, and the arm is moving

@Cuda Cody - volts to the gauge is a possibility and I guess the next step is to check wiring at the gauge.

[Chryco Psycho]

is this on the Cuda or Charger ?

[303 Mopar]

is this on the Cuda or Charger ?

Sport Satty

[Chryco Psycho]

you should have a pulsing voltage , averaging 5 v
do the oil & temp gauges work ok ?

[303 Mopar]

you should have a pulsing voltage , averaging 5 v
do the oil & temp gauges work ok ?

Si, all gauges work except fuel (there is no oil gauge).  However, when the car is running with lights on and you hit the brights the temp and fuel go all the way to the right to the point where you can not see the needle.

[Chryco Psycho]

only with the lights on ?
Ground issue power is looking for a ground through the guage circuit

[303 Mopar]

only with the lights on ?
Ground issue power is looking for a ground through the guage circuit

Only with the lights on and only with the car running.

[Chryco Psycho]

Is the pc board behind the gauges grounded properly ?
could also be at the rear light & or TS switch , sounds like the brakes are grounding through the park light circuit & when the lights are on it has nowhere to go but through the dash / gauges