I recently bought a 1991 New Holland 455C backhoe in really good condition. However, before using it I want to check all the fluids, change the oil, and lube everyplace there is a grease fitting. Got the oil changed and started lubing the grease fittings (bought a Ryobi battery powered grease gun on Home Depot.com. Got it on sale at a great price and it is worth every penny.). Had to replace a couple of the fittings and most of them took grease easily. However, I have several that refuse to take grease even after removing the fitting and cleaning out the packed grease. I will be working on it again tomorrow and would like any suggestions as to how to clear those fittings and get them to take grease. Any suggestions?