I review my note (also amended my post for future search), it its exactly as per Jim said.

The floater work well outside the tube but bind when it it. Slightly out of round. I roll it slowly like a cigar and it did the trick.

I tested the resistance of my fuel sender.

On empty, it reads 67 ohms.
On full, it reads 2.7 ohms.

Does this mean the sender is good or bad?

Good.

Then it is most likely your gauge. remove and re-flow the solder joints and insure the terminals ar clean and tight. especially the ground

Ok, I'll try to pull the gas gauge.

The gauge works VERY consistently (from F to 1/2) and never flickers or jumps.
Wouldn't this mean it's not a connection or ground?

Is there a thread on how to resolder the gauge internals?

Yes, but while you are there take care if it all.

I'm having the exact problem, what was the fix?

Even though it's a 5 years old thread, I do remember what it was in my case.

The floater would jam at half way so it would never show full tank.

The tube was a bit out of round, so I roll it (very carefully) like a cigar and that fix it.

You can check this by taking the floater apparatus out (very fragile) and move the cork up and down along 2 thin wires on each side. The gauge should react accordingly.

As I documented in this thread, the sender float was not blocked. The video shows the gauge needle travel at both extremes of the sender float. The sender was not the problem, nor was mine out of round. Pretty sure I never replaced the sender.

The fuel sender worked fine when I removed and tested it.
I can tilt it in both directions, and it freely travels unobstructed.
It registers the proper resistance at both ends of travel. At the bottom it's 67. At the top it's 2.6
So, I was told the problem lies in the gauge itself.

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I have reused the gasket several times. No issue.
Mine was still perfectly rubbery as there is no heat like a crispy valve cover.
If there is no leak, opening it will not create one.
I had a spare on hand, but didn't use it since it was identically pliable to the replacement.
After a few more times of removing the sender, I used the new gasket, but really didn't need to.

I then hooked up a 5000 ohm potentiometer to verify the gauge worked fine.
Ok, I attached a 5000ohm potentiometer to the harness plug that the sender normally connects to.
In other words, the potentiometer is now replacing the fuel sender. It is not hooked directly to the gauges.
Recall, my fuel sender correctly sends 2.7 to 67 ohms. This poentiometer sends 2 to 5000 ohms.

Since it's 5000 ohms, when I calibrated the poentiometer to my multimeter, the slightest turn on the knob would put it past 100 ohms. Using the poentiometer in place of the sender, the gauge swept the entire E to F range. What does this tell us? My gauge goes below 1/2 and to E when there's a LOT of resistance (like 100's of ohms) but it seems the sender's 67 ohms is not cutting it.

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So, it seemed to be an issue of incorrect resistance being measured. I think I cleaned up the contacts at the fuel gauge itself and saw an improvement.
When I re-tested, the needle would drop to about 1/4 when the sender float bottoms out. That was close enough for me and I buttoned it back up.

To remove the gas gauge, first remove the adjacent gauge , and then push fuel gauge out from the hole next to it. Easier.

Here is some more fun reading, if inclined
http://forums.pelicanparts.com/porsche-911-technical-forum/847863-fuel-sender-fine-open-fuel-gauge-itself.html

I haven't inspected the gauge or it's connections yet.

"Bench testing" the sender gave me the same results. Full gauge with the float at the top (3.5 ohms) and half full with the float at the bottom (69 ohms).

Gauge reads empty with the sender disconnected.

Disassembled the sender and discovered the low fuel light switch is corroded and inoperable.

After cleaning the wires and re-staking the connections now the gauge will now read 1/4 tank when the float is at the bottom.

New sender delivered tomorrow (5/21), will post results.

Not to hijack someone else's thread, but, my 69 911 will register full, after 30ish miles it drops to 3/4, then quickly to almost empty. It sits there steady until I am almost empty. New fuel tank and sender. I took out the sender and hear it sliding freely. Idea's??

My clueless guess is that the new sender will also read 1/4.
Did you clean the contacts on the fuel gauge, or just the sender?

At the bottom it's 67.
At the top it's 2.6
Does that mean you're getting prematurely high resistance?
Did you clean the contacts on the fuel gauge ?

I agree but would like the low fuel light to operate.
I looked at the gauge and can see no corrosion, connectors good and tight.
I see a place for adjustment on the gauge, will try that after the sender is in.

Thanks for this post, I’ll be following along as I have a very similar problem.

I had the same problem where the gauge hung up at 1/2 tank. I replaced it with a new one from our host which worked like a champ for a few fill ups and now it hangs at 3/4 tank. Couple of questions:

Is it really safe to test the sender outside the tank with gas fumes coming out of the tank and the possibility of an arc from the sender?

If the sender worked at first and not now, should I just get another sender, or are there other fixes?

Quick,
The sender does not arc, but lay something over the gashole to feel safer.
That's weird that your replacement sender worked perfectly at first
That feels like it sort of rules out your fuel gauge contacts needing cleaning.
I guess I would test the sender and clean the gauge contacts anyway

Thanks for this advice. I cleaned up the terminals that connect to the sender (even though they were already pretty clean) but I didn’t check the gauge. I’ll get on it.

You could have a helper tilt the sender with wires still connected and view what happens on the gauge. Confirm the gauge shows 3/4 even when sender is at bottom of travel. Once that is confirmed, clean gauge contacts, and then perform the initial test again.

After I replaced the sender the gauge would go down to 1/4 tank but still not go any lower. I loosened what I thought was an adjustment on the back of the gauge, re-tightened and the gauge started working correctly. I feel like there was a poor connection inside the gauge.