Another gas gauge problem....
 

OK....so mine goes no higher than the 1/2 mark. It will start to drop once the tank is half full and register empty and the low fuel light comes on when the tank corresponds to that which is on the gauge.....

I have swapped senders AND gauges. I have pulled the sender from the tank and turned it upside down and observed the gauge go to FULL.......once the sender is in, bolted down, fill the tank....1/2 mark and no more.....

WTF?

I had an identical problem. I had an internal short in the gauge. Since you have swapped gauges, I would guess the wiring has the short - the green wire on the back I believe (there is a red and a green wire attached to the back of the fuel gauge) that runs to the sender might be shorted to ground somewhere along the line. Try an ohm meter from the green wire to chassis ground (edit: after disconnecting the sender)and see what you get. Good Luck.

Mike,

I don't have a sending unit in front of me to examine, and my memory stinks, so take this post as just a guide to point you in a general direction to look. If you can get the gauge to read full, by turning the sender upside down, it shouldn't be a wiring problem, right? The wiring hasn't changed; only the orientation of the sender.

It sounds like the sender float isn't wanting to travel the last half way up the tube. So, I'd go looking for reasons it would have this problem.

I'd make sure the tube is not installed in such a way as to distort it and put something in a bind. If you have a fuel level in the tank higher than halfway, but below the level of the sender hole, and you loosen the bolts holding the sender, does the level change?

I'd also make sure that the top of the tube is ventilated to the tank, so the tube can't trap air in the top and become air-locked. I can't remember what the top of the tube looks like, so this may not be an issue, but I'm just thinking out loud here.

JR

The float is probably hanging up on corrosion or cruddy deposits on the slidewires. Disassemble and clean.burnish the slide wires with an abrasive ink eraser.

oldie but goodie.

I ran out of gas...and my gauge told me I had 1/4 of a tank.
Running out clogged up some stuff.

I replaced the sender, fuel pump check valve and Fuel filter.
I may replace the FPR, and damper...but that is a different story now.

Car now starts.
But, the fuel gauge shows me empty, with a new sender.
I removed the gauge...all wires look correct.
The gauge will go well below empty when the key is off.
I removed the gauge from the dash, and with the key on, I remove the green wire from the gauge.
It does go to the key off position of way below empty.
it does pop up to empty with the key on, green wire plugged in.
No lights.

I removed the plug, and even took the lid off the plug.
It can only plug in one way on the sender...and that seems correct, physically it cannot plug in any other way.

So...not sure what todo here.
I may go remove the plug again and ground out the green wire.
I believe that should make the gauge register full, and if that works..my issue might be a weird brand new sender not working (shocking that a new part would never work)

I still have the old sender...and I got used to its odd reading.
I will go see if I can clean out the old one and get it working properly.

Is there a set of values I can use to test both senders? something on a bench test?

Oh, is the gas tank grounded somewhere? It looks like the sender uses a ground tab to one of the wires, which implies that the tank itself is grounded...
Where is that ground wire? Maybe it just needs some cleaning?

Rich

Update...still hunting.

when I remove the plug from the sender and ground out the brown wire...gauge goes to full.
Im going to remove the plug cap again to make sure the wires are properly oriented in the plug.

When looking from above, wiring loom at the bottom.
Brown is bottom left
Green top left
black/red is top right

Weird.
I grounded the wire, gauge works fine.
I plugged in the old sender, flipped up upside down ( full tank) that worked
Flipped it down, empty, lights on, all good

Plugged the wire back into the brand new sender, which I did remove the locking pin on….nothing

Unfortunately I just filled up the tank.
I went for a drive to burn off some fuel…started to downpour.

Another day….

Rich

It sounds like your new sender is not working. Factory part? Aftermarket? Counterfeit?

Maybe there is a little corrosion on the original sender and it got stuck at a quarter tank for a little bit.

You might try running it again and keeping an eye on it, cross checking it with the mileage driven and knowledge of the usual fuel economy you get. You could probably tell if it sticks again at a quarter tank, before you run out of gas again, if that’s what you’re paying attention to.

New sender will be swapped for the old one.
I need to go burn some fuel because I just filled it :)

Rich