I have a problem with my fadal pallet changer on a 96 4020. The clamp pump has stopped working. The oil cup ran low while it was turned off with air connected and the pneumatic pump must have cycled through the night. I took the pump apart and it seems to be able to function fine. When I put the air line on, I use to hear a thumping for about 5 sec while the pneumatic pump locked the pallet into place. Now it does not thump. I am open to suggestions.
Verify that you have bled all of the air out of the lines. You may just have a pneumatic lock. Also verify that the actuating cylinder is freely operating. Make sure that the relay is functioning to trigger the pump.