Marker - part name
Black - needle guide
Red - pin
Green - pintle tip
In this picture the needle guide has 3 basic functions; to support the pintle in it's movement, to control the return rate, and also to control the allowed vertical movement of the pintle. If the tolerance is lost between the nozzle and guide, the pintle will stick open, foreign debris is often the cause. Removing material from the upper edge of the needle guide, also known as the stroke-limiting collar, will increase the allowable vertical movement. The pintle tip can also be ground to increase the dead volume in the nozzle tip if in a VCO style, or blind-hole if in a Sac style.
0.015" difference in pintle tip length.
0.010" removed from the stroke-limiting collar.