Gas Gauge Wrong - Best Place to Start

[Jack O.]

I know there are lots of posts on this subject and I have read most but still wanted to ask this in the hope of getting advice on which end to start. My gas gauge registers Full when full but too quicky drops to less than half a tank when it really has more. Empty seems to be pretty close to empty but it gets there too soon also. Does this indicate anything so far as whether it's more likely the gauge, the sending unit, bad connection, etc.?
Thanks,
Jack

[Jack P.]

Re: Gas Gauge Wrong - Best Place to Start

I know there are lots of posts on this subject and I have read most but still wanted to ask this in the hope of getting advice on which end to start. My gas gauge registers Full when full but too quicky drops to less than half a tank when it really has more. Empty seems to be pretty close to empty but it gets there too soon also. Does this indicate anything so far as whether it's more likely the gauge, the sending unit, bad connection, etc.?
Thanks,
Jack

Hi Jack,

It is the nature of the beast. My gauge has been off (reads like yours) for the last 42 years. If the sender does not leak, don't touch it.
Repos are junk, and even if you get yoursrebuilt, it is no guarantee that it will be right on.

Are cars are easy to check, just look in the tank. When I get near 1/4 I know I should look.

Jack

[Jack O.]

Re: Gas Gauge Wrong - Best Place to Start

Thanks but I'll have to try something - I can't deal with looking in the tank anymore.

[Jack P.]

Re: Gas Gauge Wrong - Best Place to Start

Thanks but I'll have to try something - I can't deal with looking in the tank anymore.

Here is what you can do. Two people needed. One with a small arm to reach in near empty tank and move float by hand. Or you can use a gripper (used to pick up soxs etc when you can't bend over) and grab float and rod and move through range of motion.

Watch gauge and see how it moves. It will show you where the error takes place. The problem is most often in the sending unit. Just the rapid movement may clear the contacts.

Next is to take out sending unit and have it restored. You can hope that it will fix the problem. Leaks from the gasket and problems with repros can be not fun.

You can ask for a name in forum for who does it.

Jack

[Jeff A.]

Re: Gas Gauge Wrong - Best Place to Start

I am going to be trouble shooting my Camaro fuel gauge.
Here was a helpful thread - not sure if Corvette is the same.

http://www.camaros.net/forums/showpost.php?p=1579191&postcount=2

[Paul J.]

Re: Gas Gauge Wrong - Best Place to Start

Jack O.

You've probably noticed that older American cars are notorious for inaccurate fuel gauge readings. Like Jack P. says, most of the time it's the sending unit. If his idea of "exercising" the sending unit does'nt solve the problem (or really just make it better because it will never be accurate), you should replace the sending unit. Stay away from the reproductions. Here is a thread discussing it.

https://www.forums.ncrs.org/showthre...+unit&uid=4341

Paul

[Jerry B.]

Re: Gas Gauge Wrong - Best Place to Start

Can't find the back set in order to locate that tan wire? Great article

[Tim T.]

Re: Gas Gauge Wrong - Best Place to Start

Jack,
Some people think the "corn" in the gas is causing problems with the sending units. I got an authorised GM restoration sender for my '63 that is supposed to work with ethanol and for the first time the gauge is accurate. See www.kandbcorvetteproducts.com
Tim

[Jack P.]

Re: Gas Gauge Wrong - Best Place to Start

Jack,
Some people think the "corn" in the gas is causing problems with the sending units. I got an authorised GM restoration sender for my '63 that is supposed to work with ethanol and for the first time the gauge is accurate. See www.kandbcorvetteproducts.com
Tim

My unit like others has been off long before corn, however, if this unit works well and does not leak, and is accurate , then great.

What is the cost, the site does not really function for online buying

Jack

[John H.]

Re: Gas Gauge Wrong - Best Place to Start

I am going to be trouble shooting my Camaro fuel gauge.
Here was a helpful thread - not sure if Corvette is the same.

http://www.camaros.net/forums/showpo...91&postcount=2

Jeff -

C1 and C3 have the same standard 2-wire GM gas gauge circuit as the Camaro (except C1 is 0-30 ohms and C3 is 0-90 ohms, like the Camaro), but midyear Corvettes have a totally unique 3-wire powered voltage-divider circuit not used on any other car (a "failed experiment", if you will). Link below covers the totally unique diagnostics required on a midyear; the Chassis Service Manual is no help - it just says to substitute a known-good sender and see if the gauge works.

http://www.lbfun.com/warehouse/tech_...rFuelGauge.pdf

[Tim T.]

Re: Gas Gauge Wrong - Best Place to Start

Jack,
I bought mine from him @ Carlisle. For C2s they are $69
Tim

[Ronald L.]

Re: Gas Gauge Wrong - Best Place to Start

Those from $80 and less are the China junk that generally read wrong. BTDT.

Before you install a C2, make sure the resistance in the up position is 90 ohms and zero in the full down, if not return it as that is the root cause of the problem.

The only one I found that worked and works perfectly was the real one from GM with a modern day resistance sender card, if you have not been in fuel system engineering you might not know what I am referring to, but its the card we;ve had in vehicles since about 1990 or so. They run about $300 but they are spot on: 5 gallons in 1/4 full, 5 gallons in 1/2 full reading, 5 gallons in 3/4 reading and another 5 to a full tank = reads full.

Novel concept.


These cards can be calibrated precisely and are ROH resistant,

And for the disbelievers out there, I was there when they started with corn flakes and it destroyed the resistance coils, took the tern coating off, entire fuel system clogged - it is just a matter of time before they fail.