When my fuel light comes on I have between 2.5 and 2.75 gallons left in the tank. The bulbs that illuminate all the warning lights (i.e. seatbelt, airbag, etc.) are the same small wedge-shape bulbs. I'm not sure if they can be removed from the base nor am I sure of the part number. If you want to see if the bulb is at fault, pull the gauge cluster out and switch the low fuel bulb with another one you know works as the sockets are all interchangeable. And in answer to your original question, the low fuel light does not come on to 'test' with the ignition.