Ecm no power for 30-45 sec

[Bhodges]

I have a 5.7 mercrusior and when I turn the key on it will not turn the fuel system or fire for 30-45 sec. then the ecm still doesn’t have fire to it. It first cranked and ran then it shut off and hasn’t ran sence. New motor I changed the oil pressure sensor and don’t know were to go from here. It also is not firing anymore. What can I do

 

[bondo]

Ayuh,..... Check the key switch for power,.....

The red wire should be 12v all the time,....
The red/ yellow is the start circuit,....
The purple wire is ignition,....