Your fuel sender unit (measures the amount of fuel in your tank) is banjoed or the wires going to it are disconnected. Have a look at the top of the petrol tank for two wires which connect to the fuel sender, they're obvious enough probably black & green wires. Are they connected?
If they're ok then have a look at the sender unit. It should just screw into the tank & easy enough to take out. It works a bit like the float in the cistern of a toilet in so far as the more fuel you put into the tank the higher the float rises. Check if this moves freely up & down. Connect the wires to the sender unit & switch on the ignition. You should see the fuel gauge moving if you raise the float arm, if you don't then the unit probably needs replacing.
steo, June 2009
