Another thing to consider is that the fuel return line goes back to the top part of the tank. Is it possible that once the fuel level drops below the return line the engine stops?
I'm not sure if the return line can also feed the injection pump on your engine, if the return line only goes to the injectors then I'm off track with this line of thinking.
Will the engine re-start if you remove the tank cap, wait a few minutes, then bleed and go for a start?
Sean