Hello
After swapping three engines into my car, it will not fire up. Everything needed for it to fire is there, but it won't!!!! uuuurrrrrggggggg

1st transplant had a bad cylinder, second had a bad head and now the third which was running before it (car) was rear ended it then became a donor for my car.
what can it be? Computer is fine, spark is there ....??????
Thanks in advance
Pedro