Hey mate this is because of a faulty fuel level sender , Mine would also do that and when you get all the digital bars flashing at you this is because the guage isnt getting a signal from the sender.
I actually managed to fix one of mine by removing the sender and spraying WD40 on the moving parts ie the float and shaft and re-installed and this fixed the problem.
Big Rob wrote on Mon, 30 May 2005 23:33
Hey guys.
I'm having trouble with my fuel gauge. Its never accurate, even to the point off showing a completely empty tanking when just filling up. Also sometimes when filling up it will flash a few times then show that the tank is empty.
Has anyone had any problems like this? Know how to fix this?