The fuel pump shouldn't go out with a clunk, at least mine didn't. Unless it fell off...
An idling engine also contradicts that theory. Not impossible, though. Does it start with external starting gas? Can you measure the fuel pressure?
The last time my M3W stopped with a clunk it was a snapped cam belt. The time before that it was the original compensator that disintegrated.
Is the drive belt ok?
Do let us know how it works out. Good luck!
