My first baby won't crank up
 

So hello everyone glad to be here but guys I need some help I bought a 2004 350z my very first one always wanted this car so when I bought it it had and engine knock I did care finally I got my hands on this car so I the past I've put motors in with out a problem so I bought a JDM motor for it I put it in went to start it and it won't crank first thing I did was check fuses then went back over all connection I used my wire harness from the old car everything plugged up with no issues then I checked the starter it's good but it's not getting the signal down that black wire please help I have no idea what going on now thanks in advance

I don't think anyone on here is going to be able to give you the precise solution to your "I've swapped in a new engine, and now it won't start" question.