Recently bought s14 kouki, won't start

[MistraL]

I recently bought a 1997 Nissan 240SX SE, from a man who was working on it for someone else, he was replacing the thermostat. After he replaced it and filled it with coolant they started it and he said it all at once jumped and stopped running, he figured the timing had jumped or the chain around the cams had jumped teeth. I pulled the upper tensioner and it is really soft, could that of really caused what he said? any ideas would be greatly appreciated.