The lever at top of the filter has 3 positions. Center (straight up & down) is off. There is an "Air" and "ON" or Run position. Turn lever so small pointer end of lever is at "Air" position the crank engine for a few seconds, then move pointer to ON position and try starting. If it does not start, repeat the process. Just changing filter should not have drained fuel out of the injection pump so should prime quickly.