Enrico,
That's exactly what I thought and why several others that suggested you check power at the pump before purchasing a new one. It's most likely a bad relay or bad connection in a junction box between the relay and the pump. Check this with extreme care... better yet get one of your electrician friends to help. If you have a bad wire nut connection you can be dealing with a live leg of 240 volt wire that is not where it needs to be. Judging from the photo's of your box this is not a very neat installation which means somebody without the proper skills has been messing around in there. A qualified electrician would not leave all those wires dangling around .
I hope this helps.
Chris