[pugslyx234]

Thanks for the info, I pulled my tank and checked the unit it was loose at the connection inside of unit.

[Red Box Rebel]

1968 GTO with a missing red fuel gauge indicator needle!

I have read every post in this thread, but I am unable to say the red fuel gauge indicator is pegged at empty or full since I cannot see the red indicator needle at all.

I have unplugged the tan wire at the rear trunk connector, but still no sign of the red needle. According to numerous previous posts, leaving the tan wire unconnected and hanging free should cause the gauge needle to peg all the way to full. After performing this test, the red indicator needle still did not appear on either side of the gauge.

I need to know how to test the gauge without removing the dash if that is possible. I would like to eliminate the fuel gauge as the problem before removing the tank sending unit.
In recapping, I cannot tell if the red indicator needled is pegged beyond full or pegged way below empty. It simply cannot be seen at all. Any help and/or suggestions will be greatly appreciated. Thank you

[Greg Reid]

Do you have a volt meter?
Check to see if you have voltage on the tan wire with the switch on. If not, the wire may be grounded somewhere or it may be broken. If that's the case, nothing you do back at the tank will matter.
If you have a meter, check that, report back.

["QUICK-SILVER"]

I'd ground the tan wire and try to force the guage to empty.

More than 90 ohms, open, unplugged...will let the needle go out of sight past full.
0, zero ohms, dead ground...Should put the needle on empty. The needle isn't suppose to drop below empty. Guage should have a stop peg (not visible) that stops the needle at E.

If force empty doesn't work in the back, move inside and try it at the front ribbon harness connector.

Clay

[Red Box Rebel]

Will check with the volt meter and get back to you. Thank you

["QUICK-SILVER"]

Originally Posted by Red Box Rebel

Will check with the volt meter and get back to you. Thank you

If it does show voltage...Hook it straight to a good ground source and see if the needle goes to E.

Straight to ground is what the sending unit does when you're out of gas.

Clay

[Red Box Rebel]

Checked the tan wire in the truck connector and it had 7.65 volts with the key on engine off.
I pulled the tan wire from the dual connector plug and took the multi-meter positive lead to the tan wire coming from the gauge and the negative lead to a good ground with a jumper wire between the tan wire and the plug connection so the circuit was complete.

With the circuit broken and the positive lead to the tan wire coming from the gauge and the negative lead to a good ground, it read 0.00 volts.

As stated earlier, the red indicator needle is still nowhere to be seen.

["QUICK-SILVER"]

Originally Posted by "QUICK-SILVER"

If it does show voltage...Hook it straight to a good ground source and see if the needle goes to E.

Straight to ground is what the sending unit does when you're out of gas.

Clay

Originally Posted by Red Box Rebel

Checked the tan wire in the truck connector and it had 7.65 volts with the key on engine off.

What happened when you hooked the tan wire straight to ground? No meter required for this test. And no danger in touching it straight to a good ground.

You can do an ohm test on your sending unit with the meter. Harness unplugged..One probe to tank wire and the other probe to a good ground. If the sending unit is good...You'll get a reading from 0 to 90 ohms depending on how much fuel is in the tank.

Clay

[Red Box Rebel]

When the tan wire is hooked straight to ground nothing happens with the key on engine off. The red indicator needle is still not visible.

Have not done the ohm meter test yet. I assume that it must be performed at the sending unit itself.

Thank you

Paul

[Red Box Rebel]

Okay, I have resolved the missing fuel gauge red indicator needle problem. What I learned is that the needle was pegged all the way to the right (full side) but could not be seen since it was way past the full mark.

Based on the suggestions of Quick Silver and Greg Reed I removed the tan wire from the plug at the inside rear of the trunk. At first I grounded the wrong side of the wire. I grounded the side of the wire coming from the sending unit rather than the gauge.

Once I corrected my mistake, I grounded the tan wire coming from the gauge to a good known ground. With the key on engine off, the missing red needle moved from way past full to the completely empty mark in the gauge.

So, now I know I either have a bad sending unit (its only 51 years old) or the ground is bad at the tank. As soon as I have time to check under the car, I will report back what I find.

The good news is that the gauge works and the wiring to the rear harness is also good.
The information post previously was spot on and allowed me isolate the problem. Thank you to all who contributed!

[Greg Reid]

You are on the right track now. If you go back through this thread, you may recall that several have found that the factory connection at the ribbon cable stud can corrode or rust. You may be able to clean that up and get it working.

[Greg Reid]

From post #26...

[Shiny]

Greg, I had not seen this thread before but it's a great trouble-shooting reference.

If I went to the trouble to pull the sender to clean a bad connection, I'd find a way to solder that strap to the pin or replace the press-on nut with two threaded nuts that can clamp the strap. Even two pal nuts might be more reliable.

The image you just posted appears to be an inherently corrosion-susceptible electrical contact design. I have never touched a sending unit but assume the metal post is the "positive" or "signal" end of a variable resistor that passes through the body and is insulated by the washer, correct? Or is there a plastic sleeve to insulate?

Yes, cleaning up and putting back together will restore a degraded connection but it may not last another 50 years.

[Greg Reid]

Shiny, I've never torn one apart so I'm not sure how the insulator is arranged for the brass stud. Soldering it is an interesting idea but it might take quite a lot of heat and may damage the insulator if you got it up to the needed temperature.
As for the original vs a new one, there have been some reported issues with the new ones not lasting but a few years. Due to that, I think some are preferring to keep the old ones.
I put a new one in my '68 when I replaced the tank and it's been trouble free for 7 or 8 years now.
I do have to say though, my old one worked fine but at the time, never hearing of the complaints that I heard later, i tossed it for a new one. New tank, new sender, right?.

[Red Box Rebel]

The ground wire coming from the sending unit is connected to a good ground. Still need to droop the tank to see if the contact at the sending unit is still good.

Most likely the sending unit is bad and will need to be replaced.

[Greg Reid]

You probably have about a 50% chance of it being the connection. If it is, I'd save it if possible. Some folks have reported problems with the new units, although I haven't had a problem with mine. It's been installed about 7 years.

[Red Box Rebel]

Originally Posted by Greg Reid

You probably have about a 50% chance of it being the connection. If it is, I'd save it if possible. Some folks have reported problems with the new units, although I haven't had a problem with mine. It's been installed about 7 years.

UPDATE:

Dropped the Tank over the weekend. All connections are good and surprisingly had no corrosion and no rust. First time the tank was ever down/out of the vehicle. Original sheet was laying on top of the tank.

Have determined that the sending unit is bad and will need a new one.

Tank is in good shape with only minor surface rust in certain places. I plan to replace the straps and attaching hardware.

Will report back when everything is re-installed and working properly.

[Greg Reid]

I used a Spectra... I think that's the spelling... At any rate, got it right over the counter at the parts store.

[Red Box Rebel]

Originally Posted by Greg Reid

I used a Spectra... I think that's the spelling... At any rate, got it right over the counter at the parts store.

I was able to get the Spectra Fuel Sending Unit at Autozone for 53.99. It looks exactly like the original. After I recondition the tank, I will install the new sending unit and let you know how it works.

[Greg Reid]

Good deal.