Fuel Gauge Reads 3 Different Levels Depending on Key Position? - 1968 Charger

[Indetrucks]

Hey y'all, have an interesting scenario with my fuel gauge.

With a full tank of gas, here are my fuel gauge readings:
-Key off, fuel gauge drops to E as it should.
-Key in ACC position (left) gauge reads between 3/4 and full.
-Key on (not running) gauge reads slightly higher than ACC position around the full mark.
-Key on and car running, gauge reads extremely high, pegged much past the full mark.

Side note, I looked under the dash and noticed the voltage limited wasn't grounded at the male spade connector which comes off the backside. When I grounded that spade, the fuel gauge reads empty with the key in the on position.
It appears the fuel sending unit is on the newer side and is grounded correctly. I am unaware of brand or when it was installed.

Wondering if I should start with installing the IV4R Solid State RTE limiter or what I should start checking first?
Thanks!

 

[R413]

Sounds about normal. My 60's/70's mopars do the same thing.

When it's not running it has whatever your battery voltage is. New batt is 12.6-12.8. Older batt 12.1-12.4.

Now start the car and it could be anywhere from low 13 volts to mid 15 volts depending on your parts and the RPM. That's why it reads higher when running it has more voltage.

 

[Indetrucks]

Sounds about normal. My 60's/70's mopars do the same thing.

When it's not running it has whatever your battery voltage is. New batt is 12.6-12.8. Older batt 12.1-12.4.

Now start the car and it could be anywhere from low 13 volts to mid 15 volts depending on your parts and the RPM. That's why it reads higher when running it has more voltage.

Thanks for that. But it reads full-pegged past the full mark when running and a full tank. When the fuel level is empty, it still reads 1/4 on the gauge. Was thinking it could be the voltage limiter or the fuel sending unit arm needs to be bended up?

 

[dadsbee]

Gotta remember that the fuel gauge is really just a volt meter !

 

[Jerry Hall]

Newer fuel sending units most always need adjustments, and then they are only accurate at full and empty.

 

[R413]

Should go past full when full, not stop there at full, again a normal thing. The E mark is the one to have correct. So take out the sender and bend the arm to get that right.

I bought a car once the guy bent the arm so full was right on the F mark, but you could drive for 50+ miles on E, plenty of fuel at the bottom of the gauge, backwards to me.

 

[dadsbee]

Like ^^^ says. I don't care about anything other than how quickly I need to find a gas station..

 

[Indetrucks]

Should the voltage limiter be grounded at the male spade connector coming off the back of it? From what I've read, yes but when I ground it, my fuel gauge reads empty

 

[R413]

Should the voltage limiter be grounded at the male spade connector coming off the back of it? From what I've read, yes but when I ground it, my fuel gauge reads empty

Then don't ground it, easy fix!