1963 fuel gauge problem

[Ruedi K.]

Hello,

Yesterday I drove a bit with my 63 Corvette. The fuel gauge was reading normal at around 1/8, close to empty. After that, I filled the tank completely to the top (as much as I could), turned the ignition key and the fuel gauge jumped to empty. After a bit of driving it even jumped below empty, far to the left side.

My question is, what could cause this? Is the fuel gauge defect or may it be the fuel tank sending unit (I replaced that about two years ago).

Before refueling the fuel gauge was working properly. Quite strange.

Thank you for any helpful advice.

Rudy

[Terry D.]

Re: 1963 fuel gauge problem

First thing to check is the ground. On earlier Vettes we run a separate ground wire from the sending unit on the tank to the frame

[Ruedi K.]

Re: 1963 fuel gauge problem

Hello Terry,

I just checked the ground. Seems OK. I think I will have to drive around a bit, until the tank is half-empty and watch the gauge. I think it could be the fuel sending unit. The gauge worked the weeks before, so this is what seems a bit strange. I have to say, I never filled the tank that full before, I always left some "air".

Thank you.

Rudy

[Domenic T.]

Re: 1963 fuel gauge problem

Ruedi,
If the car sat for a long time the fuel varnishes the coils (resistor) in the sender, all but under the slide. Then when the slide moves along the coils it doesn't make contact.
That's a possibility if your ground is good. Ground the sender center wire and the gauge should read full with the ignition on if it is good.

DOM

[Duke W.]

Re: 1963 fuel gauge problem

Leaving air in the tank promotes moisture absorption. Especially if you store the car in winter, the fuel tank should be full to keep moisture from contaminating the fuel.

There should be some troubleshooting advice in the 1963 Corvette Shop Manual, and my experience is that the wire wind in the fuel sending unit can build up deposits, which leads to flaky gage readings.

I have had some luck with adding Chevron Techron to the fuel, but most of the time removing the fuel sending unit, carefully bending the tabs to remove the cover and thoroughly cleaning the wire wind with acetone and lightly dressing the wiper with a nail file was required to get the gage to behave properly.

Duke

[Ruedi K.]

Re: 1963 fuel gauge problem

Thank you for the replies and advice.
I will check the fuel sending unit when I empty the tank then, if necessary, I will replace it

Rudy

[Domenic T.]

Re: 1963 fuel gauge problem

Ruedi,
I am out of the country and can't take a look but you should be able to see the sending unit from the fill. Someone will chime in if I am wrong. I think you can spray carb cleaner on the metal housing and hope to reach the coil & clean it. Carb cleaner (can spray) is not friendly to the O-ring that seals the unit but if you dilute it with gas it should't. Damage it. Also I think you can excersize the unit with a wire.
Problem is that a empty tank is not safe and ANY static can cause an explosion. Not common but it can happen. In a nut shell as always you MUST be static free. Same rules as when you fill your tank at the gas station. I weld gas tanks and there are things that can be done to eliminate a problem. I think if you are carefull it is only a little more dangerous than removing the sending unit from the bottom as the gas fumes rise.
I did about 8 sending units this year ( only 2 vette) and found the coils dirty and the scraper tension bad on all but 1.

DOM

[John H.]

Re: 1963 fuel gauge problem

Ruedi -

The attached file will walk you through the operation and diagnostics of the unique-to-63-67 Corvette fuel sending unit, which was essentially a failed experiment; a 2-wire powered sending unit with a Whetstone-bridge voltage-divider circuit that was used only on the midyears, and was never seen again. Its circuit diagram is also attached. The "Fargo" reproduction sending unit referred to in the article is no longer available; if you have an original AC sending unit, John Wolf & Co. can rebuild/restore it better than new.


C2FuelSender [800x600].jpgMidyearFuelGaugeArticle.doc

[Ruedi K.]

Re: 1963 fuel gauge problem

Hello

Just came back from a car show. Thank you for all the useful advice and the diagram. I will fix that problem next winter.

Rudy

[Rob M.]

Re: 1963 fuel gauge problem

maybe leaking float?

[Ruedi K.]

Re: 1963 fuel gauge problem

I will let you know what it was, when I get round to fix it.

Have a nice week.

Rudy

[Dan S.]

Re: 1963 fuel gauge problem

Rudy

The same thing happened to my 65. The gas gauge was working until I filled the tank completely. It immediately stopped working. Using the testing methods suggested on this forum confirmed it was a bad sending unit but I'm hesitant to fill the tank completely even though a new sending unit is in place.

[Ruedi K.]

Re: 1963 fuel gauge problem

Hello Dan,

Thank you for the reply, that you had the same experience with the fuel gauge. I guess I will just replace the sending unit and afterwards I won't fill the tank completely again.

Rudy