will return to nearly the same compression sequence after the starter is released - meaning the lift pump will many times still be "on the cam" to some extent after a starter run. You may have to rotate the engine by hand a bit to get the pump off the cam. Even so, the lift pump lever is a poor way to pressurize the system. It often takes an interminable amount of pumping to actually clear a system. It would take only about ten minutes to install a bulb in the fuel line (or an electric pump if it's in the budget) right after the tank. The beauty of this is, it will automatically "bleed" the system for you. The fuel pump (whatever it is) simply makes fuel AVAILABLE to the injection pump, whatever surplus fuel (and air) are in the line are forced past the injectors and down the return line to the tank. So, pumping the bulb etc clears your system of air in a hurry.

If the engine would start and idle before you changed the filters - I would have to think the problem is still in the fuel delivery system. While the 2GM20 is my very favorite diesel engine (of that displacement) I nonetheless know it to be a persnickety feeder that does not digest air well. I doubt the compression has gone bad since you changed the filter. Do be sure you have pushed down mechanically on the compression release levers after using, to return them to their proper position - a good friend of mine just spent a week fighting his engine before discovering one of his release levers had not returned to it's compression mode.

"He who perseveres conquers!" Perseus