Abstract: A lower filter for a fuel injector includes a disk having an annular shape and including a plurality of filter holes. The disk is positioned upstream of a valve guide of an internal valve assembly without contacting the valve guide. The disk prevents internally generated contaminants contained in fuel flowing through the filter holes from reaching a valve guide area and a sealing area of the internal valve assembly. By installing the lower filter upstream of the valve guide and without contact to the valve guide, interference with the guidance and reciprocal movement of the valve is avoided. Application of the lower filter in fuel injectors may reduce the occurrence of injector failures by reducing the number of stuck open conditions in injectors and by reducing the number of hydro lock engine incidents without interference with the valve guide.