Unless it's different from a normal pump the pulley is a press fit on the pump shaft. There are pullers mad that grab the groove on the pulley hub. Normal way I take one off, off the truck, is a flat punch in an air hammer, applied to the end of the shaft. It will walk the pulley off pretty easily. Never tried it on a pump that I needed to save though, I'm not sure that it doesn't do damage to the pump internals.