I have lots of experience with engines in general, both diesel and gas, but not with that engine in particular.
That said, a gas engine compression tester will not work. You need one that tops out at about 500PSI or more and with the correct fitting for your injector, or glow plug(if equipped) hole.
Assuming that you bled the system after removing and replacing the injectors, I would suspect timing. What does the engine have for a cam/injection pump mechanism? A belt, a chain, plastic gears.
You really need a manual or someone with lots of experience with that specific engine to know how to check fuel delivery timing to start with. I say to start with, fundamentally you are on the right track in checking compression, but compression typically does not go away all of a sudden.
Best of luck,
Certified, ASE Master