The Gas guage goes up and then down and the gas light goes off

check the sending wire to see if you have a bare spot
if you don't know where the sending wire is we don't know either
as what year
model
etc

It sounds as if the fuel tank sending unit is faulty. This is a small float connected to a variable resistor on the fuel pump/sending unit assembly. Unfortunately this assembly is fairly expensive (over $300) and the fuel tank may need to be removed to replace it.

A loose connection on the sending unit could cause the problem but also moisture in the tank in cold weather could also be a factor in which i would add fuel line antifreeze to a full tank of fuel..........Hope this helps you out.

sounds like fuel pump is good the floater may need replacing or the wire that reads the floater may be loose

Your sending unit inside of the fuel tank is probably faulty. Unfortunately you have to drop the tank to change it.

Sounds like the sending unit is bad in the tank.

The sending unit in your tank is bad replace it.

The most likely culprit is the sending unit in the tank. They are relatively easy to change, as long as you don't have much fuel in the tank. It's a mechanical unit that has a float that raises and lowers with the fuel level, however with age, the floats can develop leaks and no longer float, of the electronic portion of the unit can go bad and not register the proper level. They are replaced and an entire unit, so it doesn't matter which happened, you will need to change the fuel tank sending unit.

open circuit in the fuel level sensor. mounted in tank. as the fuel level in the tank starts to drop the arm will move past the dead spot on the sensor and the gauge will start reading again.i dont recommend diy replacement of the fuel level sender.