Peter,
Even if the pins are blocked by the bushings, you can remove the Zerk and run a drill through the bushing...it's bronze or brass and very soft. It doesn't hurt a thing if you drill into the pin a bit.
This will guarantee a path for the grease. Reinstall the new, good Zerk and pump away. As you drill, watch for the chips to change from brass/bronze to steel. That's when it's time to stop drilling. A small dimple in the new pin won't hurt a thing.
Cousin Stuart
