Other: Fuel Guage

[57studechampion]

Ok you guys. You have always gave me good advice to this point.

On my 56 2dr Champion sedan. My fuel gauge has NEVER worked right o n this car.

Here is the situation.

I only have one wire to the tank. The Gauge reads full with the key on and wire on sending unit connected.

If I disconnect wire on sending unit it goes to 1/2 full even with key on. So I thought maybe I had wires reversed on gauge. I switched the wires and reconnected to sending unit and now the gauge shows full again, even though I have driven 139 miles on this fillup

Any other suggestions or recommendations to check? Is there a way to check the gauge with a volt meter?

I am open to all suggestions

Again Thank you for all of your advise in advance.

[TWChamp]

Can you see any markings for the gauge terminals?
On my 51 Commander fuel gauge one terminal is marked "IGN" and the other has no markings, so I know it goes to the tank unit.

[57studechampion]

I will look at it and see. If they are connected properly than could it be the gauge or sending unit in the tank?

[TWChamp]

When you remove the wire, and the gauge only drops to half full, it seems like a dash gauge is most likely bad.

[57studechampion]

Thanks for the advice. I was thinking the same thing.

[bezhawk]

First thing to rule out the gauge is to disconnect the wire from the gauge, not the sending unit. It would seem you have a ground in the wire to the sender. The gauge unit see the hot on one terminal, and it is isolated from the completing the circuit to ground. The sending unit is the ground. You can get a 33 ohm resistor and hook one end to the non power terminal on the gauge, and the other end to a good ground. The gauge should read full. What you do NOT want to do is hook up a straight wire to ground to check the gauge. The resistor limits the current so it won't fry the hair thin wires inside the gauge.

[doofus]

That bit of cardboard on the back of the gauge is marked ever so faintly,study it closely. Luck Doofus

[57studechampion]

Well guys I have FINALLY done it. After owning this car for 5 years I have a gauge that appears to be working. I put a new gauge in it and as Doofus said it was marked on the cardboard spacer which side is the IGN.

I put in the gauge and started the car. With the key off it shows empty. With the car running it SLOWLY moved. It showed 1/4 tank. I have 170 miles on this tank. I will take the care out tonight, since no chance of rain, and fill it up and see what the gauge shows at that point.

As someone mentioned at one time I would rather it show empty with a few gallons left in the tank over the opposite of it being empty and showing that I have gas on the gauge.

I will let you all know later.

[tim333]

The gauge is supposed to work slow, it doesn’t just jump to whatever level is in the tank.

[TWChamp]

My 50 Land Cruiser only shows 3/4 when the tank is full, so I removed the tank unit and found it is a universal unit. I had to bend the arm to get the correct travel, but it still only reads 3/4 when full. I bought an NOS dash gauge on Ebay, and I bought an original tank sender when I was at French Lake the other day. When I get back from the Gilmore Museum I will change out both units in hopes it will read full.

BTW, both the new universal tank unit, and the original unit read from 0 ohms to 100 ohms.
Were the original corks coated with Shellac, or was it something else?

[57studechampion]

Well there is a vast improvement. It took only 9.9 gal. The gauge reads 1/2 on level ground and 3/4 on an incline. Maybe I will try to adjust the float in the tank. This winter project.

[TWChamp]

Well there is a vast improvement. It took only 9.9 gal. The gauge reads 1/2 on level ground and 3/4 on an incline. Maybe I will try to adjust the float in the tank. This winter project.

That tells me your tank isn't full. The float should be at the very top when it's actually full, so it wouldn't change on an incline.

[StudeRich]

/Cut/BTW, both the new universal tank unit, and the original unit read from 0 ohms to 100 ohms.
Were the original corks coated with Shellac, or was it something else?

Just Shellac, BOTH the Shellac AND the Cork will be eaten or compromised by the Alcohol in most of our Fuel.
The best floats are Brass (Ford) or Plastic replacements.

[57studechampion]

I think that the tank is full. It kicked pack when I filled it.

So I agree with StudeRich. It is most likely the float assembly.

Like I stated earlier. This will be one of my winter projects.

Thanks again for the imput