I would need to see a diagram. If it is one where the engine has to be removed from the case to work on it, then I suggest buying a new one.
If you take the bar off, sometimes the oiling path will be clogged with caked sawdust. Examing the holes in the bar and the hole where the oil is supposed to be coming out of the case.
Some have a mechanical pump that is under the chain clutch. Others use vaccuum to pump the oil.
Post a model number and someone might be more familiar with it than I am.