Debris in the water can get into the tell tale bypass circuit and cause this on again off again stream. The best way to clear it is to remove the side cover, take the hose off completely and remove the nipple fitting in the block. With the lower end in a trash can of water, run the engine at 2500 rpm. If the pump is in good shape the water will GUSH out and soak you down instantly if you stand in the wrong place. This gushing will definitely clear anything that may have been trapped behind the hose nipple and restore permanent flow.
Crunchy21 is right about the fitting in the cover. Also, the rubber hose should be replaced every 3 years or so. It will get hard over time and small particles will have a harder time working their way through the bends. The hose should be supple and limp not stiff with bends permanently "set" into the hose.
Also, the hose only gets routed one particular way. If it is routed improperly, it will be squeezed partially or completely closed when the cover is put back. Note how it is routed before you pull it off.
A rule of thumb is that, if you can plug it on the fitting easily while reinstalling the side cover, it's probably routed incorrectly. When properly routed it's a bit of a pain to put it back on the side cover nozzle.
Good luck.