Remove the hose from the rear-facing nipple in the fuel filter head and turn your key switch to the run position. Do not crank the engine.
See how much fuel flows from the hose. It should have a full pulsing flow. If it is just a trickle, remove the water separator from the machine and unscrew the bowl, removing it.
Remove the plastic screen from the separator, using a blow gun with compressed air, and blow air through the hole in the underside of the head that lines up below the shut-off valve. You will probably blow debris out of the inlet elbow. When it is clear, reassemble the separator and reinstall it.
Turn the key switch back to run and recheck the fuel flow.