[ischmitz]

The DME (also called engine control unit) is the large silver box that is shown above. Logically, it acts as an OR. Either it needs to see the flywheel moving (with both sensors) or it needs to see the starter being engaged (key in START) to turn on the 2nd stage of the DME relays (the little black box).

That box has two relays combined and these are daisy-chained. The first stage turns on when the key is in RUN. And the first stage is a pre-requisite for the 2nd stage to be turned on. So you could say the 2nd stage is a logical AND. Once the DME determines the flywheel is moving fast enough (>200 RPM) or the starter is engaged it supplies the other input to the 2nd stage. And that turns the fuel pump on.

If you have issues starting the engine you need to determine what is missing: Fuel (does the fuel pump run), spark or both?

That will help narrow it down to whether it's the DME, the DME relay, one of the sensors, or the DME itself. Do some search here. Lot's of good material to read up about this. Good luck,

Ingo