To add to the description in the other posting.
The fuel is delivered under pressure from the pump in the right hand half into the fuel cell in the left side. A portion of this fuel is bled off into a "jet-pump" which uses high pressure fuel jetted into a venturi to create a low pressure which picks up fuel from the left side and delivers it back to the right side. Thus the fuel level in the right side should always higher than the left. What the designers imagined would happen if all the fuel should end up in the left side with none in the right I have no idea. I have had the filter housing in the left side pop undone on several occasions now, where the fuel ends up in the left and the pump goes dry. Usually I put the housing back together and put a self tapping screw in the bayonet part to stop it turning (not through the side ).
The other thing to watch out for is that there are two level senders and loads of pipework in the tank with plenty of opportunity for the floats to get fouled (don't ask how I know).
Shaun