Replaced the motor with what? A complete motor with accessories from a
wrecking yard? A reman long block?. If it was a complete used motor, did you
replace the computer with the one that is correct for that engine management
system? Did you miss connecting the ground wires for the systems?
Questions like yours are very hard to answer because I don’t know the skill
level of the installer. There can be many causes for a "no start/run"
condition, but remember the ECM is in charge of all the fuel/ignition
functions, it has little to do with the engine itself.
Chino Autotech Inc.