Is it possible to calibrate or adjust the fuel gauge? Tank, lines and sender are new. There's no gas in the tank yet. I have just gotten to installing new wiring harnesses and the dash/console is next.

I would like to have all the gauges 100% working and reasonably accurate, Is there some way of checking the fuel gauge for accuracy before I put any gas in the tank? Thanks for any help, Rick

 

Hi Rick,
I really think that the configuration of the arm, (it's bend), the float is on controls the accuracy of the gauge….if we can take for granted that the gauge and rheostat on the sender are working properly.
I replaced my sender and found the float wasn't as buoyant as the original float, so I changed back to the original float.
My hand and wrist are small enough so I could reach in the 71 tank and cycle the arm to make sure it was operating the gauge properly before putting much gas in the tank.
Good Luck!
Regards,
Alan

Here's the bend in the arm on my original sender.

 

Thanks for the reply Alan. That's what I'll do. Maybe I can use a hooked rod or something to reach it. No problem removing the sender to re-bend the float rod if it proves necessary since the tank is still dry. Thanks, Rick

 

Hi Rick,
You do need to verify what ohm the rheostat is on the sender to make sure it's correct for your gauge.
I'm really not sure how much it might have changed over the years.
For my 71 it's 90 ohms.
Perhaps Willcox can verify for your 69.
Regards,
Alan

 

i put a new sender in my 72 couple months ago,
when tank was full ti brim, it only showed just over 3/4 full on gauge.
so drained tank into drums, removed sender, and bent the arm a tad, re-installed and re-filled tank.
repeated until i was happy with reading.
when tank was full i could use a piece of wire rod and still move the arm up and get a full reading.
so i thought the float wasn't as floaty as well.

 

Hi Alan- 0 - 90 ohms for all cars 1963-1982.

To the OP.. if you watch the video we did on the fuel gauges, you'll see a quick way to test the actual gauge is to apply power to it with no ohms input. This will make the fuel gauge to to right above the right hand rivet. Then ground out the ohms and you should go to empty. (the exact readings are shown in the two pictures on the left below).

The next step as mentioned above is to verify the float is all the way down and the sender is reading o ohms. With the arm fully elevated the sender should read a min. of 90 ohms. The adjustment of the arm is critical to getting a correct reading.

Willcox

 

Thanks to all who replied and thanks to Ernie for the testing info. Rick

 

Not knowing if this will apply...but it has bit me ONCE in the 'backside' several years ago.

When I went and tested the new sending unit manually...the gauge worked PERFECTLY...the 0-90 ohms and all that were great.

I installed it and put fuel in the tank to check for leaks and that was all good.


Then I added more fuel and when I came back and looked at the gauge...it was not reading correctly due to the amount of fuel I KNEW was in the tank...and when I removed the fuel cap...and looked into the fuel tank...the FLOAT was actually NOT FLOATING on top of the fuel....it was suspended half way.

SO...I drained the fuel tank...removed the NEW sending unit. I removed the FLOAT on the OLD sending unit and also the float on the NEW sending unit and took them over to my paint scale which is SUPER SENSITIVE....to the tenth of a gram.....and weighed them....and the NEW FLOAT was 50% HEAVIER. So I put the original float on the NEW sending unit...re-installed it and added the fuel and the float was ON TOP of the fuel and read correctly.

NOW...with every NEW sending unit...I verify the weights of the float.

DUB

 

As long as the gauge shows that the reading is changing when the needle is between E and F, you should be able to determine how much fuel is left at any gauge marking or recalibrate it with resistors installed in the signal line and/or from signal line to ground.

Hook it up 'as is' and fill the tank. It will probably read above the Full mark...which is good. Drive the car until it reaches the Full mark, then top off the tank and record how much fuel it took to fill it. That is the amount of fuel you have in "excess" above the Full mark when the tank is filled.

Drive car again until it is at the 3/4 mark, then fill tank again. Amount of fuel dispensed is the amount of fuel used from a filled tank to the 3/4 mark. Repeat at 1/2 tank, 1/4 tank, and E mark on fuel gauge to determine exactly how much fuel is used at each mark on gauge.

Note: Know the actual capacity of your tank before you start this process. If you get close to using up all the fuel in the tank BEFORE you get to the "E" mark test, you may want to carry a gallon of fuel with you during that part of the test.

If the gauge reading never gets to the Full mark when filled OR never gets to the Empty mark when fuel is gone, you will need to bend the float arm to get more 'travel' in the float in the direction of the problem (bend float arm upward if gauge doesn't read high enough when full; bend arm down if gauge doean't go to "E" when fuel is low).