u/Suicidalpenguin24

Hi all, I’ve got an 04.5 Sierra 2500hd I just put a replacement junkyard motor in after it cracked two pistons. Got everything back together, primed the fuel system and whatnot, and now it just cranks but won’t turn over start… it sputtered up once but then died almost immediately. No notable codes but my live data is showing 0rpm when cranking. TIA