With the regular strainer grids on with my Intex 1500GPH filter pump it is hard to notice much water going in or coming out. This seemed especially odd, since when you put the hose adapter on for the skimmer, there is a LOT of suction. It turns out that the shape of the inside of the fitting is like the bell of a trumpet. It distributes the pressure over a wide area.
My current solution is to put the skimmer hose adapter on the OUTPUT of the pump. I now have a fairly strong blast of water into the pool. You just have to remember to put the regular strainer grid back on before people swim.