Fuel gauge reads full or empty 1988 Bronco II with tachometer

[IIBRONCOS]

This problem has been going on for a few years. The fuel gauge will read either full or drop to empty. I thought I had a float filled with gas, so I bought a new fuel pump and sending unit. If it matters the Bronco II is all original with 62,000 orig miles.
The problem is still there. I am getting tired of using the trip meter and want the gauge to work properly. I connected the original sending unit assembly today and tested the gauge and it reads full when the float is in the full position, but even if the float is let down just a little, like (1/4") the gauge drops to empty. It does the same with the new sending unit assembly. I am pretty sure it is a bad gauge, but before I take the dash apart I wanted to make sure I wasn't overlooking something. If anyone has a new fuel gauge for sale please let me know. I guess I should also replace the gauge voltage limiter. Looking for and appreciate the help.

 

[Uncle Gump]

Have you tried just cursing at it... ?

 

[Uncle Gump]

Did you try sweeping the sender with an ohm meter?

 

[IIBRONCOS]

Have you tried just cursing at it... ?

A number of times.

 

[IIBRONCOS]

Did you try sweeping the sender with an ohm meter?

How do I do that?

 

[Uncle Gump]

Ohm meter... just to make sure the sending unit is good.

 

[Uncle Gump]

Good post by RonD...

If we are just talking the sending unit then engine or tank size wouldn't matter just Year

Up through 1988 Ford fuel level senders(AND GAUGES) used 73-10 ohms, 73 ohms EMPTY, 10 ohms FULL
1989 and up use 16-160 ohms, 16 ohms EMPTY, 160 ohms FULL

So an early gauge won't work with later sender, and visa versa
Wiring was the same

The Float arm attached to the sender is important because its related to tank size, tank height really
You want it to show EMPTY accurately, since inaccurate FULL won't strand you, lol
So you want the sender to be at its limit(73 ohms) when float is within two inches or so of the bottom of the tank, this is called the "reserve", lol, so you can set the "reserve" by adjusting float arm based on lower end of fuel pump on the assembly
Two inches might be 3 gallons left, but this does have to do with tank width and length, so your call

Same for FULL but if you set lower limit and the upper limit doesn't allow float to move to the top of assembly its not a big deal, gauge just shows FULL until you burn a few gallons of fuel, MOST vehicles are that way when new, lol
EMPTY is the main one to get right

You can read about them here: https://www.fordification.com/tech/fuel-sending-units.htm
And maybe you can fix your original one

 

[IIBRONCOS]

Ohm meter... just to make sure the sending unit is good.

Today I swept both sending units. The newer one that has been in the tank reads out fine with no dead spots as I move it slowly from empty to full. I am getting about 70 ohms on empty and it slowly changes to about 10 ohms on full. I reinstalled the newer unit. I have a full tank of gas and right now the needle goes to the full mark.
I will keep tabs on it as I drive to see how the gauge responds.