Ford Escort fuel level sensor Mod. 90

Greetings to all. I take the opportunity to introduce myself. I am Joaquín de Arroyo Seco, Santa Fe and I am 30 years old. I recently acquired a Ford Escort Mod. 90. I still have to make some things to leave it in perfect condition and to solve one of them is that I go to you.
The problem I have is the following:
the fuel level indicator does not mark. There are no variations in the information on the board, it is dead in a empty tank (although it seems obvious notice that the tank has some fuel). The other problem I have is that I cannot locate the access to it from inside the cabin under the rear seat. Remove the armchair but I didn't find anything. Could someone give me a hand with this topic? I thank you for your time.

Welcome, Sposito! : You are going to have to get under to see if from there you access the aforar and its wiring, which may be bad for the years and, or the float has been blocked, or the wiring/ connector has been spent on the use, or the wiring/ connector is evil, if everything is fine, you will have to open the board instruments to see if it is not connected, already in the last case; To change the picture. Luck!!