Fuel guage not working on bmw 318i 1996

relay is usually found under the hood and fuel pump is in the tank
more and likely it would be a fuel pump test your fuel psi. first

could be a problem with the security chip in the key.

Your intank fuel sending unit is failing and needs to be replaced. This can, and should, be purchased as a complete unit includuing the fuel pump and filter. You have to go into the tank anyway so why not replace both. Thank you, Dana

this is caused by the gas gauge sending unit in the gas tank being an open circuit, pull the tank and replace it.

Fuel pump may be getting weak. If pressure is not high enough the injectors wont open.

the only problem is the floater of your gas tank.It is easy to be fixed all you need to do is to take the back seat off and you will going to see the upper portion of your gas tank there's a circular or square portion plate that have a 4 bolt's on it and a electrical wire just loose the bolt's and pull the floater up, then you will see there it's electrical mechanism just clean it by using a sand paper to clean the bronze part then turn on the key switch, move the floater up and down check the gas gauge. it is not pricey though if you want it to be fixed by a mechanic.

You do need to replace the guage sending unit in the gas tank, u must remove the gas tank, this is not really a job for a DIYer.

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.

Sounds like the Fuel sender unit in the fuel tank needs replacing however you may want to check that the electrical plugs are contacting properly,Check that the gauge is working by putting a piece of wire from the sender unit wire to the chassis,at the fuel tank sender unit plug,Turn ignition on while watching gauge if it moves toward fill turn ignition off and remove wire to chassis.If gauge moves it means from the fuel tank to fuel gauge is intact and not your problem.