12.7 turns over and stops

Usually when it does this water is on top of piston. Is it low in coolant?

 

Injector Cups are usually bad when this happens. What year 12.7? If it is 2005 and newer you can replace cups without removing head. If not the head has to come off. You might be able to turn the engine backwards at the accessory drive and get it to start after doing so but don't cut it off until you are ready to fix it because it will happen again.

 

Your hydrolocked. Fuel or coolant on top of piston. Now you have to figure out what one and why. Dont keep trying to start it as you can bend a rod doing so.

 

Very possible. Cracked head, injector cups, head gasket , fuel, coolant.wont really know for sure till you dig deeper.

 

If it was hydrolocked, you'd be able to feel or see cushion in the turning of the engine, meaning when you come to a stop you can turn it by hand and see if bounce back to the current location. If it's a firm stop, like it hit a wall I doubt it's hydrolocked. If it does have water or fuel on top of a piston it will eventually work its way down, you wouldn't think, but it will and will eventually turn over. I'd inspect anything you worked on, perhaps you left a wrench somewhere, or have a bolt lodged into something. Or there is the possibility that something failed when you shut it down. If your unsure, you can remove the inspection plate on the top left (drivers side) of the engine and inspect the gears with a borescope, or you can remove the accessory drive on the passenger side and inspect In there. Roll the engine by hand til it stops and listen for clunks and if you hear a noise, try to narrow it's location. And FYI engines can still be blown up and turn over. When you get a locked up engine that you want to sell, sometimes it will turn one direction and not the other, sometimes an engine has to turn a certain direction to hit whatever is locking it in just the right manner, like a pawl in a ratchet binder. It will click over the pawl in one direction, but lock in the other.