D12 no start

Hey all we have a D12 in the shop here that was towed in. Driver reported it started smoking, and the engine started running rough. He pulled over and the engine died. It has under 600,000 miles on it. Here is what we have come up with. We ran the compression test on VCADS. According to VCADS 1,2,3,6 have no compression. We really havent used VCADS in the past to run compression tests. Is it an accurate test? No odd noises coming from the engine when cranking. No pressure or smoke coming from the crankcase as we crank it either. Sounds to me like bent valves. Anyone seen this on this type of engine before? Valve cover is off. Dont see anything out of the ordinary up there. Inspected the gears down as far as I could see, all of the gears look to be in good condition. Lastly, it has not had any recent valve adjustments or anything like that. Any guesses on cause of something like this? Thanks!

 

I may have not made my statement completly clear. There is no metal on metal or any type of metallic noises when cranking. BUT if we are trying to start it, it will hit on a couple cylinders then spin then hit again. Kind of like it is lacking fuel. If we are cranking the engine but not trying to start it(pulling ecm fuses, or doing a cylinder compression test) the RPM of the engine spinning changes. It seems like its slowing down only on the two cyulinders making compression and then speeding up on the ones that arent.

 

I know it is such a uncommon problem. I had the same thought. But the camshaft seems fine. Its just ashame. We take great pride in keeping our stuff in good running order. Then something like this happens. And it seems like such a rare failure.

 

Pablo - It is cranking over the way like you said.

As for watching the cam/rocker/valve operation with the valve cover off, we did that already. From up top everything seems to be running fine.

There hasnt been any valve lash adjustments done on it. So I am a bit stumped as to what would cause this failure.