Fuel Guage Fluctation

[M W.]

Trying to find out if my fuel guage is doing what is normal or not. I had my 64 instrument cluster restored last year and not sure if it's off or my fuel sending unit is going wacko. During normal operations no matter the level of fuel the guage needle seems to have a lot of constant movement. I know that as the level of fuel moves around that the fuel level arm floats up and down but it just seems excessive. I think maybe it's time for a new sending unit but advise of others is appreciated.

Thanks in advance,
Craig

[Joel F.]

Re: Fuel Guage Fluctation

Before you replace anything, I'd run a test ground from the ground wire on the sender. This is a common resolution for this issue.

[M W.]

Re: Fuel Guage Fluctation

Joel what will this tell me?

Thanks,
Craig

[John D.]

Re: Fuel Guage Fluctation

Joel what will this tell me?

Thanks,
Craig

Will tell you that you may have a ground issue. If you are lucky. JD

[Joel F.]

Re: Fuel Guage Fluctation

Craig,

Running an extra ground is simple and fast and hopefully will keep you from having to replace anyting.

If that does not work, try this: disconnect the tan wire at the sender. With the ignition switch on, the gauge should read full.

Then ground the tan wire. The gauge should read empty. If it only goes partway down, the gauge is probably bad.

[John H.]

Re: Fuel Guage Fluctation

If that does not work, try this: disconnect the tan wire at the sender. With the ignition switch on, the gauge should read full.

Then ground the tan wire. The gauge should read empty. If it only goes partway down, the gauge is probably bad.

That works for a C1 or C3, but not for a midyear - midyears use a totally different 3-wire voltage-divider circuit design for the fuel gauge that was a failed "experiment", used only on '63-'67 Corvettes and a few Cadillacs.

If you'll go to Barry Kimmelman's site, http://lbfun.com/Corvette/Tech/vettetech.html

Scroll down to "Instruments & Gauges", then right click on "C2 Fuel Gauge" to download my detailed technical article on understanding and diagnosing the midyear fuel gauge system.

[Joel F.]

Re: Fuel Guage Fluctation

Thanks John!

I've only done the troubleshooting on my '62. As always, I am learning something every day.

[Jimmy G.]

Re: Fuel Guage Fluctation

Craig

Clean all the contacts and connections. Sometimes helps. If not the sender may be borderline

[M W.]

Re: Fuel Guage Fluctation

Hey Jimmy I hope all is well. Looking forward to the fall Chapter Meet. I will double check all the contacts and then do the deed if needed.

Cheers,
Craig

[Ken A.]

Re: Fuel Guage Fluctation

I would bet on the gauge being the culprit.

[M W.]

Re: Fuel Guage Fluctation

John, I finally got around to following the advise from the website you provided and it's definetly in my sending unit at least according to the test provided. Thanks a bunch.

Craig

[Stuart F.]

Re: Fuel Guage Fluctation

My 63 has been a bouncer for years, but it is always in the ball park. One problem I have is a lead foot, and that makes it go from full to half full very fast. Guess I am used to such things though, as my first car (a 50 Chevy) had a 6 volt gauge with the balance of the system 12 volts, w/a 58 Fuelie engine. I had a simple toggle switch to turn on the gauge momentarily to take a quick reading, then shut it off. Only ran out of gas once, mostly due to my lead foot.

Stu fox

[David D.]

Re: Fuel Guage Fluctation

Craig,

I believe the reason the Fuel Gauge fluctuates is because of the dampening fluid. Or lack there of.

The fuel gauge has a dampening fluid internal beneth the needle that over time dries or leaks out. The reason they put this fluid in there, was so when you went around a corner or accelerated fast and gas is sloshing around, it was to dampen the potential 'fluctuation'. It is possible it's the sending unit if the resistor in it is not linear. So need to check both.

When a person has a Fuel gauge professionally rebuilt OR if they know what they're doing, can re-apply dampening fluid. This will alleviate the fluctuations. As long as you don't have wiring, or sending unit issue that also coincide with the fluctuations.

If you need the name of a good gauge guy, I would highly recommend Bill at http://www.harrisonspeedometer.com/ 561-676-3099

Hope that helps,
David

[Lenny K.]

Re: Fuel Guage Fluctation

Thanks John.....really comprehensive details....I too have a '63 "bouncer" but by the end of the week I will know why, and go from there....smile.....LK