As with any saw, the oil passage can get blocked. 1st step is to clean the bar, including the groove and the holes where the oil passes into the groove. Also clean the casing where the bar is sandwiched. Start the saw without the bar and see if any oil is coming out. If you have a manual oil button, you can pump it also. If no oil is coming out, check the tube going to the oil resovoir. If none of these items are blocked, then it is time to locate and remove the pump. It could be blocked or worn out.