When a grease zerk won’t accept grease from your grease gun, the simplest solution is to unscrew the zerk, clean it out with a wire, brake cleaner or compressed air, reinstall the zerk and try it again. If it still won’t work, you have bigger problems and may need to call in a mechanic. As a precaution and to avoid the downtime, put a few spare zerks in your machine’s glove box or storage compartment, and always wipe off the nipple of the zerk before greasing. The likely cause of the blockage is grit or dust that accumulated on the outside of the zerk and got forced inside when someone forgot to wipe it clean before greasing.
More Maintenance/Management tips from “How to Do Everything Better”