No there is nothing to realy go wrong with the pump, make sure the nylon drive gear drive by the sprocket has not worn, if this ok,check the pick up filter in the tank is not blocked, there is a less fine pick up filter to go in the tank ( the standard filter is very fine, and thick non fling oil does not pass throught it on very cold days due to its viscocity, you can thin down the chain oil, this will help) the pump capacity is governed by the throw of the shaft ( it does not just rotate, it resiprocates) it is possible to increase the throw by increasing the angle on the back of the pump shaft ( to increase the throw) this is a dealer job as it is importent not to increase it too much, and to grind it correctly as it is timed to the flat on the other end of the shaft, let me know how it goes.
Husqvarna man
January 2010