Hello, just bought this truck from a friend of mine he had a problem where the timing belt tensioner broke off and caused the engine to stall, this VG30 was out of a mercury villager and was modified by Nissan to be a non interference engine, a shop replaced the tensioner stud, installed a new tensioner and timing belt but truck still wouldn't start, than I bought the truck. Anyway

I got the engine to crank today but it wouldn't start it sounded like it was backfiring thru the TB I checked the timing marks and they didn't look like they were all lined up so I removed the timing belt and lined up all the marks, when I went to try and start it it still wouldn't start and after turning over a few times it just stopped cranking, I tried to turn the engine over by hand and it goes 3/4 of the way around than just stops like something is hitting.Any ideas on this please??

Thanks