My fuel sensor does not work it stays at the ful mark

Most fuel pumps today are sold as module assemblies which includes the hanger, pump and level sensor. The level sensor is the device used to report the fuel level to the fuel gauge. Fuel level sensors work by attaching a float to the fuel level sensor arm; when the fuel level lowers so does the float which in turn moves the sensor arm and changes the signal. Level sensor floats can be rather bulky when attached to the level sensor arm so often times they are not pre-installed at the time of the part sale. Once the new part is removed from the box, the float (whether a new one is provided or simply removed from the original unit) must be installed onto the new level sensor arm prior to fuel pump module assembly installation. If a float is not installed, the metal level sensor arm will not be suspended at the fuel level which results in an "empty" fuel gauge reading. You can read more here: https://www.yourmechanic.com/article/why-fuel-pump-replacements-can-be-tricky-by-marvin-sunderland

Was the old fuel flushed from the tank? Does it have a fuel filter that is possibly clogged? Is it possible some trash from the old fuel/ tank has gotten into the new carburetor and the float is stuck?

Sounds like your fuel pump in on it's way.

Looks like you have a fuel level wire that has gone to ground or you have a faulty fuel level sensor. Disconnect the sensor at the tank and see if that changes the level. If it does then the problem is with the float level sensor. If it stays at full with the sensor disconnected then somewhere the feed wire has gone to ground.

Sounds like the float is stuck, or corroded. Look to see if you have an access door above the fuel tank. If so you should be able to take out the fuel sender, unstick the float, or clean the sensor, and replace it

P0463 - Fuel Level Sensor Circuit High Input
An excessively high voltage is sent from the sensor is sent to ECM.

The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM or PCM.

It consists of two parts, one is mechanical float and the other side is variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.


Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)

Possible causes
- Fuel level sersor circuit harness or connectors is open or shorted
- Fuel level sensor may be faulty

Possible solution
Replaced fuel level sensor.

Hope helps (remember to rate this answer).

The gas tank sending unit has a float on it to register the amount of gas in the tank. The float is probably faulty which will cause erratic readings and is a fairly common issue with some GM units. Replacement of the sending unit should resolve that issue. As far as the coolant temperature gauge, it could be a faulty temperature sending unit or a thermostat that is stuck open or someone removed the thermostat. This will cause the engine to never reach operating temperature which in turn makes the engine run rich and can clog cat. converters and destroy some sensors.

the float assembly is part of the fuel pump assembly and is in the tank. the fuel tank will need to be dropped and call your local dealer to see if they sell the float seperately or as a fuel pump/level sensor assembly.

The fuel gauge in the fuel tank is simply a float connected to a bar connected to the sensor. Take a look at that and see if that float is stuck in one place causing a false reading.

Apparently, you jammed the sensor float attached to the pump which runs the gauge. The float must swing up and down to measure fuel level. That runs a resistor unit which varies the reading on the gauge. It is not doing that.