Re: Possible to throw a rod while starting engine ?
I have never seen a rod actually broken, Do you by chance have some big huge amperage battery?
The one thing I have seen is a cylinder fill up with coolant overnight from a blown head gasket. The next morning it wouldn't start (it hydro locked). That was the jeep I bought. I suppose if that cylinder is maybe on its intake stroke going down and it has filled with a bunch of coolant, the motor may be able to pick up enough speed to break the rod. Again never seen it though.
P1281 could point to a low coolant condition, unfortunately coolant temperature sensors read the fluid they are surrounded by not the surrounding metal temperature. As such, if its not warming up, it may not be that it is actually not warming up but that there is a big pocket of air around the coolant temperature sensor, many times pockets of air in the engine are caused by head gasket failure... again this is all speculation.
I have seen a dodge neon punch a hole in the top of the piston thanks to a piston that was rotated back off of a piston stop then cranked over (at school, not a customers car), gm products have an intake plenum that warps and fills cylinders up with coolant, this has been known to blow the starter off the side of the block, there is quite a bit of torque at play!
2005 Jeep Grand Cherokee - Gone but not forgotten!