Sudden crank not start issue

If you lost pressure when you stopped cranking, that is normal. The DME (digital motor electronics) control module will switch off the relay immediately if it no longer detects engine speed. This ensures that the fuel pump cannot continue running when the engine turned off.

Will the engine start for a couple seconds using starting fluid? If you have spark and the fuel pressure should have fired the engine, it should run unless there is no fuel injector pulse. In that case, it should still start with starting fluid.

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Fuel pressure running is around 50, so you were basically there. It should have fired.

As far as the cam sensors, we may need to take things apart to check timing. If it has spark and still won't start for a couple seconds with starting fluid, something else is happening.

Let me know.
Joe

Okay, then chances are the pump antiflow back is bad. However, that shouldn't prevent it from running. At this point, since it won't start with starting fluid and it does have spark, I would check engine compression. If there is a timing issue, it should show lower than expected compression.

Even if the cam sensors have failed, the vehicle is designed to continue running based on crankshaft sensor info.

https://www.2carpros.com/articles/how-to-test-engine-compression

Let me know.
Joe

I can't tell what I am looking at in the video. Is that a converter? What should I pay attention to?

I attached a pic of the chains. Either the one for that side has broken or the counter chain has broken. That isn't good news and explains the cam codes. If you confirm the engine is a 4.8L, I can get you the directions for replacement.

Let me know.
Joe