How did a guage become a measurement?

https://www.amplifiedparts.com/products/feeler-gauge-20-sizes
https://www.pakwheels.com/forums/t/need-a-feeler-guage-for-tappet-adjustment/161905
https://www.amazon.com/Armstrong-70-819-Piece-Blade-Gauge/dp/B0012WNIDQ
http://www.skf.com/ph/products/maintenance-products/hydraulic-tools-for-mounting-and-dismounting/hydraulic-tool-accessories/feeler-gauges/index.html
https://www.amazon.com/uxcell-10mm-70mm-Thickness-Plastic-Measuring/dp/B01MRISC7P
https://en.wikipedia.org/wiki/Feeler_gauge

You may have a unique problem!!! Normally I would say it is the sending unit- in the fuel tank!!!! But Buick LeSabre had a weird thing happen from time to time. Look closely at your fuel guage and focus on the PIN that acts as a stop for the fuel guage to not go beyond the Full mark. Make sure the pin is on the correct side of the pin!!! Sometimes the needle will somehow jump the pin on "E" or "F", and literally hold the needle in place.

Pull the float bowl and float bowl gasket off the carburetor.
Place the carburetor upside down and let the float rest against the float needle.
Measure the distance between the gasket surface located on the bottom of the carburetor to the edge of the float. On a 24 mm Mikuni card, the distance between the gasket surface and the float should be 1 inch. On a 20 mm Mikuni carburetor it should be 7/8-inch.
Bend the metal tab on the float that rests against the float needle. Bend it towards the float needle if the measurement is shallow and away from the needle if the measurement is too much.
Use a pair of needle-nose pliers, making very small adjustments to the metal tab and then recheck the measurement.

This might be more going on then just a "stuck float".

However to try to free the hung float full the tank (again) and have a with a few people shake the car back and forth, this took place on my own car.

I was able to fill it up again and fix it. Another problem may be the gauge, at times they can become over extended and be trapped, only way to fix it is to help the needle back.

Hope this helps.

The float needle has jelled fuel holding it open, rust from your tank is holding the float needle open, The float needle tip is damaged, or you have a sunk float. Take apart clean and inspect your carburetor. Replace any worn or damaged parts.

it is either the gauge, fuse,or sensor

check the cable both end (speedometer to transmission}

Bad IPC.......If u can round up a tech 2 scanner, do a guage sweep and i bet u will see the temp guage will not operate correctly......a new IPC (Instrument Panel Cluster) is really the only fix. Once installed it has to be programmed. If u need any help send me a return message.

Is it the factory oil guage? Is it an electronic or mechanical guage? if it is mechanical that means you actually have a small diameter tube from the engine to the dash area, which may have a kink or bend in it. If it is electronic then your dealing with a wire which can have a slight short in it or a bad connection. REMEMBER!!!!!!!!!

An oil guage that works properly will have up and down readings. When the RPM's increase, so should the oil pressure guage. when you are not running the engine( idleing) the guage will read lower and sometimes bounce back and forth around 5 PSI. sometimes more depending on the grade of oil, how hot the engine is and how old is the oil.

1.If the needle on the guage is stuck. you can try tapping the guage to see if the needle moves or turn the ignition on and off a few times to see if you can get it to move. If the guage drops to empty when you turn off the ignition you know that its not the guage. (note that the guage does not drop to zero when ignition is off with all cars of this age).

2. The problem could be with the sensor in the fuel tank itself. Rocking the vehicle up and down from the rear (you will need help doing this) may free the sensor level indicator ball in the tank.