I have just replaced the ECU, the black immobiliser box, and the ignition barrel and key.
The vehicle is a TJ AWD.
Car wont start. When I turn the key lights come on on the dash and I can hear the fuel pump but starter motor is not turning over and engine does not start.
I havn't replaced the door barrel and keys or the boot and glove box barrel and key yet.
I bought the ECU, Immobiliser box, Ignition/door/boot lid/and glove box barrel and keys as a matched set.

maybe try getting a new starter?

problem solved. Bad earth between engine and chassis.