It does dump the unused fuel back to the tank. If you look at the injectors, you see a line to each one which appears from the back side of the engine. It would be normal carburetor logic to figure each injector has its own feed. Then you notice that there is a fuel line between the two injectors. What you have is a pressurized loop that comes from the tank, thru the injector housing and back to the tank. The ECU signals the injector when to turn on and when to turn off. It is much more precise then the Bing CV carburetors on my old BMWs and pretty much fuss free when all the pieces work.
