Oil pump is behind clutch . However , removing clutch and pump is a bit tricky . If  oil is appearing down the side of the clutch cover , it suggests the oiler is working fine .
Maybe you just need to do a bit of maintenance on the bar .; -take bar and chain off , thoroughly clean the groove in the bar (old hacksaw blade) and ensure the small hole is totally clear .
                
 LAZYMAN
                
 August 2008