Check from the connection of the fuel unit sender in the gas tank if the gauge and the yellow light for the gas reserve work in a car electrical repairs or connecting inside the pin a copperwire.This way you are able to see if is the front fuel gauge that doesn't work or the fuel unit sender inside the tank.I had almost the same problem,from a electric blast(short circuit?i am not shure this is the right translation).This way i realize my fuel unit sender is broke.