Do you even know how
AO Gold Member
Join Date: Sep 2007
Location: South Africa
County: Western Cape
If the engine is immobilised through the ignition then it will still crank so your problem is most probably electrical, provided the engine is not seized up for some reason but to check this, do the following.
First try to turn the engine by hand. If this works, then check wiring, voltage at the starter motor, earth connections, etc. It may be a faulty starter motor, but if it fails to turn by hand then you may be sitting with a mechanical fault.
If you only replaced the engine only, and kept the ecu and alarm unit then it should start.