Not entirely sure.
Have you tried resetting the fuel cut-off switch (big rubber plunger type thing mounted on the rear bulkhead near between the brake master cylinder and the fuel filter).
Might be a timing issue - check that the orientation of the dowels in the v-shaped slot in the cam pulleys is correct, and the pulleys are correctly set with both EX marks to the rear when the bottom pulley is lined up with the timing mark above it.
Have you kept the ECU from the original engine? If so, it should work as before, but if you have fitted a different ECU, it will need security matching to the security ECU (the two units share a common code to enable disarming opf the immobiliser).