Gauge or sending unit?

My fuel gauge does not work correctly. It never quite reaches full, and shows empty with about 5 gallons left in the tank. I'm not sure if the problem is the gauge or the sending unit. I've ruled out a bad ground on the sending unit, but could it be a bad ground to the gauge, or a bad positive connection? Is it possible that the sending unit or gauge is simply broken?

 

What you've mentioned, or it could be a bad float, partially filled with fuel.

 

Before opening the fuel tank, it is good to check the electric line , it is easier. The connector to the gauge is easy to get under the dash.

I am not enough able to check myself, but a good specialist in electricity can do it.

The ohmic value is between to levels (full/empty). With a variable resistor, you can position exactly the gauge at the good position.

You move the car to make the fuel move.

Check the mass at the fuel tank before. Then you can look at the gauge (the ohm value of the gauge is known on the data book).

And then you look at the fuel tank, change the sending unit, it is 30 $.

 

My last 3 yep 3 floats have been full of fuel. I have heard you can get one from the Ford dealer parts dept. that will work. Don't know if that's true.

 

If you still have the original sender then it is likely a cork float. I believe your problem is the float arm is incorrectly set. Remove the sender and measure from the bottom of the tank to the top. Mine is 6". Then measure from the bottom of the sender mount plate to the bottom of the float at full drop. Bend the steel wire to obtain the tank depth reading and remount.

 

Yes, the ford thunder bird has a brass float.....I used it to replace the brand new plastic one on my sending unit that came with a special hole....But then I still had to adjust the float arm to make it accurate...

 

I bought a replacement Omix I believe, about a year ago for my 59 cj5 and I have an entire NOS Speedometer assembly with NOS fuel and other gauges off ebay. And I still don't really believe my gauge to be really accurate. Yes when I fill the tank the needle moves smoothly to the full mark, but it seems to stay there for days of driving, and when it starts to move it goes down quickly and 1 or 2 more days later its showing almost empty and when I fill it back up it says I was only missing about 5-6 gallons roughly half a tank when the needle was saying 1/8 tank. and when needle hits Empty it really is empty. and you better find a spot to pull off and don't try any hills or you get a air bubble in the system.

 

"If you still have the original sender then it is likely a cork float. I believe your problem is the float arm is incorrectly set."

I have heard that the cork floats were sealed with shellac, but ethanol fuel destroys that coating, and the cork gets heavy.

 

I have the original sender and mine was the arm aswell. it got a grit on the potentiometer it rides on and always read empty. but now after 5 years its fixed and working.

 

Sometime this week I will pull the sending unit and take a look. I have some contact cleaner I can put on the potentiometer, and I will make sure the arm is angled correctly.

 

Yes They fit just right ...I got my off e-bay,it was for a ford. It made half of brass and some kind of foam.

 

Ford float numbers here, and a "how to."

<http://www.gudim.com/ReplacingCorkFloats.html>

A "heavy" float would explain your symptoms.

 

But so would a miss-bent and too short arm that doesn't allow the float to come up to the top of the tank and hangs at the limit before the tank is actually empty. Would be checking that before anything else because if it reads full for an extended time, the float is probably ok.