Factor

Hi all!,

Stock 69 fuel sender...I know if we ground the sender if goes to FULL...is there any way a faulty sender can show "1/4" tank...when empty??

Thanks,
Ron

20mercury

Wilcox has great writeup on how to test fuel sender:

http://repairs.willcoxcorvette.com/c...el-gauge-info/

My 2 cents; a sender could show 1/4 of a tank if the wire to the float is bent incorrectly so that when the float is on the bottom of the tank the sender is in the 1/4 full position. I would think you could empty the tank, get a flashlight and see where the float is when your gauge reads 1/4 full.

Hope this helps.

The13Bats

My 72 had a few odd gas gauge issues, it would do this show more fuel and yet the tank would run empty, then it stopped working altogether and the gauge showed like 1/4 tank no matter how much was in it,

I stuck my hand in and grabbed the rod the float was on to see the gauge work of I moved the arm, the float was hung on something, it wouldn't allow it to go down all the way and then the float stuck on it, This was over 35 years ago and the details escape me but I really recall it being a sheet metal screw through the tank threads were catching the float but that makes zero sense as how could a screw be in my tank?

but I bent the arm a little and it never hung up again...

But being that the sender is just changing the ohms for the gauge to read it could read wrong just from being worn out....

0Willcox Corvette

If you ground out the ohms wire the gauge should go to empty, if you leave the ohms wire off then the gauge should go to full as shown below. Test the gauge function first...

Is it possible for a faulty sender to register 1/4 tank? Sure.

If the resistor is blown on the back of the gauge then the dash unit will work between empty and 1/4 tank but no further.

Upload that page posted to the right, all the info you need to find your issue is in there. http://repairs.willcoxcorvette.com/1...-unit-testing/

Willcox

Factor

Thanks! Great info!

MORE INFO....this weekend i noticed... on hard accelerated cornering, it rolls to between empty and 1/4 tank...gonna look into the issue this weekend...

happy to hear more thoughts too! Thanks all!

R

0Willcox Corvette

If the gauge reads correctly and will pass the open and grounded ohms test it's working fine. A working gauge that is over responsive is usually caused by the gauge housing has lost the dampening fluid from inside the actual movement. When this happens there is no resistance to the quick change of hard accelerated corning.

Our old friend Roger got me working on a solution to that by using a capacitor to slow down the change. The end result or my own conclusion was that by the time you go to the trouble of doing this you could have purchased a new or good used gauge. Dampening an old gauge that has lost the fluid is just putting a band-aide on the issue, eventually the gauge will fail all together.

Willcox

The13Bats

Another win by Willcox. ...

Factor

OK!

First...Willcox is awesome!

Second
Watched the video...my findings.
-sender wire working fine...ground to empty, off to full.
-float is not bent or moving off
-dampening fluid gone...movement with cornering or acceleration
-it reads full when full...but seems to be about 1/4 on empty...

I believe my resistor could be off...or not holding at a full 90 ohms
(didnt pull the gauge dash to find out)...BUT according to Willcox, they are not sold...so maybe make one...?

thanks!
R

7T1vette

If you substitute for the wound wire resistor that came on the fuel gauge, it needs to be capable of handing the current put to it by the fuel gauge circuit. It was resistance wire wrapped around an insulator so that it could handle the current and also so that it could dissipate heat easily.

The resistor would need to be a 90 ohm, 5 watt ceramic [body] resistor. It would need to fit into that space without interference with other components.

0Willcox Corvette

It can not be a resistor going out... It's impossible!!! A gauge with a blown resistor will only move between empty and 1/4 tank and would fail the first test

If the gauge pegs and goes to full with the resistance/ground test then the only things it can be would be a float sticking or a failing sending unit, or the analog movement inside the fuel gauge is tanking. Considering that you get heavy sway when cornering this could be your issue. So the next time you get your fuel gauge to where you think it should be below a 1/4 tank, pull the wire off the sender and take an ohm reading, it should be less than 18 ohms.

Willcox

7T1vette

If the gauge goes to "E" (or below) with a grounded sending unit wire but never goes below 1/4 full when connected, the sending unit must be bad or the float is getting stuck at 1/4 full (and will drop no farther).

The gauge is not the problem is it goes full scale to the right with "open" sender wire and full scale to the left with "grounded" sender wire. Those tests PROVE that the gauge is working fine.

0Willcox Corvette

w/Charlie.

I just re-read this and the op stated the gauge went to empty with the grounded test.. if the gauge goes to empty when grounded and full when left open then the gauge is not the issue. I can assure you the resistor isn't the issue...

That just leaves the sender.

Willcox

Factor

hmmm...great ideas!

will look into the sender float arm...

thanks!
R

Factor

OK! played with the float arm...it moves the gauge as it should.

does not appear to go all way to EMPTY, even with assistance.

I drove to actually "run out of gas"...got it to between E and 1/4...appeared to be almost done. I did not run out of gas, but monitored it by looking inside. I decided I was almost finished when I saw the netting 1/2 wet with fuel, and 1/2 not. That was perfectly between E and 1/4.

I believe I have an 18 gallon tank...filled up with 16.5 gallons---TO THE BRIM.
thus about 1.5 rolling around. NOT sure how high one fills this kind of tank?

those are the findings. All working fine otherwise. thanks!!!

7T1vette

Not sure whether the sending unit rheostat is defective or the float arm is just bent wrong...

Factor

agreed.

other than the slightly off reading...it works great.

I am gonna watch the gauge, and keep her filled. no need to get crazy until something happens.

THANKS all!