Hi,
What belt are you referring to? If it is the timing belt, certainly if it isn't timed properly or tight, it won't start. Actually, if this is a DOHC or 24-valve engine, you will cause internal damage if the timing isn't correct.
If it is a SOHC, there are no interference concerns. I attached a pic below of a SOHC engine. Is that how you had the timing marks aligned?
Let me know.
Joe
See pic below.
Jul 13, 2023 at 12:31 PM