No start

I have been pulling codes indicating problems with the camshaft actuators for quite sometime, but just recently my car just stopped on me and wont start back up. It cranks but does not start. I towed it to a local shop and was told that it had jumped time and this was determined by doing a compression test which resulted in no compression at all. I am curious to know if this is a viable way to diagnose the timing and if no compression indicates more of a problem with the cylinders. I have not taken to another place just yet. I was looking to get a little insight on the procedures of checking the timing without taking the engine apart.