Either it is sucking in air or really dirty fuel filter. Fuel filter heads wear out fairly regular on these engines. Change the fuel filter and make sure the Water sensor at the bottom of the filter is not leaking(another common problem). Pump the primer and get all the air out then pump till it is firm. If that don't fix it you can either rebuild the filter head with new O rings or replace it. Several vendor on this site sell both for a lot less than dealer.