Could it be that the engine shut off valve is engaged ? Keeping the fuel shut off. I'm puzzled that the starting fluid didn't have an affect.

When using the monarch primer. Pump it till it starts to squeak and give it another 20 pumps.
And yes go easy on the starting fluid.
Here's something you can do. Loosen the nut on the injection line at the injector. Get into the car, step on the gas pedal to the floor. Crank without waiting for the glow plugs to warm up. Crank for 20 seconds. Turn off key. Check the injectors to see if any diesel is coming out the injection line. If so tighten the injection line nuts. If not repete the process until you do. If no fuel is present after 3 or 4 attempts then I'd suspect the fuel shut off valve. The fact you changed the fuel filters must have something to do with it not starting. Nothing else makes any sense. The starter in my old 85 turned the motor over rather slowly but it always started.
Roddy

Sent from my SM-G900I using Tapatalk