1963 - fuel is full but gauge is reading 3/4

[Dan C.]

I have verified the gauge is accurate by testing it out of the car and again while (now) installed using the John Hinkley "quick check" outline . I have also verified that the needle placement on the gauge is centered.

When the tank is full, the gauge will read 3/4 and then seems to progress down accurately toward empty as driven. I replaced the sending unit a few years back and the same thing occured; same reading where it never exceeded 3/4 and otherwise shows normal operation. Although I never run the car out of gas to see the reading on an empty tank.

Is this a function of bending the float arm to get a "full read at full"? I have topped off the tank now. Do I need to burn it out to manipulate the float arm or do you suspect an electrical problem?

I'm not real good in this area so any advice is apprecated!

Thanks,

Dan

[Timothy B.]

Re: 1963 - fuel is full but gauge is reading 3/4

Dan,

I can't answer your question except to say this exact same problem has been discussed in the archives.

I can tell you the ground circuit for the sender and guage runs through the dash harness to ground at the birdcage to the left of the radio. The birdcage grounds to the frame with a ground strap at the drivers side firewall body mount.

[Dan C.]

Re: 1963 - fuel is full but gauge is reading 3/4

Thanks Timothy. The birdcage ground to the left of the radio is secure and clean metal is touching clean metal. The birdcage to frame appears to never have been removed so each contact was scuffed and I soaked the strap in wd40 over the weekend and scuffed contacts as well. It is on secure although I was surprised to see it only clips onto the birdcage!

[Joseph K.]

Re: 1963 - fuel is full but gauge is reading 3/4

I put an aditive in the 69 gas tank and let it set for a while and the guage began to work corectly again. I do this with the 01 also.

[Dan C.]

Re: 1963 - fuel is full but gauge is reading 3/4

Do you remember what it was? I am hoping to avoid putting in the 3rd sending unit!!

[Edward B.]

Re: 1963 - fuel is full but gauge is reading 3/4

If manipulation of the float lever when the sending unit is out of the tank results in a "full" reading on the gauge, it would seem as if your problem is mechanical rather than electrical. Perhaps in its present configuration the float is reaching the top of the tank before the sensing end of the lever is reaching the spot where it will electrically register 'full." I would suggest bending the lever so that the float sits a little lower relative to that part of the lever that contacts the sensor. Think of it as a toilet tank that becomes full without shutting off the fill valve because the float has run out of travel room; the solution is to bend the lever to lower the position of the float that the valve will shut off. It's the same with your gas tank; if the float has run out of travel room it must be adjusted downward so that the gauge reads full at the same time the float gets to the top of its arc.

[Ronald L.]

Re: 1963 - fuel is full but gauge is reading 3/4

Dan, There is a good recent trail of info on this from earlier this year.
First - have you measured the resistance at MT and Full?

If they are off you will never get to to a full tank reading, or will be showing full at half a tank.

If you find my posts on this specific topic from March - the repop senders all of China origin measured 150 ~ 200 ohms at full when the system (and the original spec of the resistor car) is 90. You should be able to do this by taking a relatively MT tank, getting a stick, pushing down and having some one read the ohm meter. Same thing hook it and bring it to full. If the full reading is greater that 90...

Let's put it this way, anything off at the MT and full limits will produce wrong results in the car.

Been there done that!

[Dan C.]

Re: 1963 - fuel is full but gauge is reading 3/4

Edward,

Well stated and I understand that concept . Let me work on it!! Thanks for your help..

Dan

[Dan C.]

Re: 1963 - fuel is full but gauge is reading 3/4

Ronald, Let me find your post from March and review before I proceed. Thanks. Dan