TM 10-3930-671-24 STEP  14  Loosen  the  head  locking  screws  and  remove one screw (Figure 3.14). FIGURE 3.14. STEP 15 Invert the pump and holding fixture in the vise. Loosen  and   remove   the   head   locating   screw   using   a 7/16" deep well socket (Figures 3.15a and 3.15b). NOTE On  pumps  without  an  advance  system,  remove  the cam locating screw and proceed to STEP 19. FIGURE 3.15b. STEP 16 Tap the advance screw hole plug lightly with a hammer to loosen (Figure 3.16a). FIGURE 3.16a. Loosen  and  remove  the  advance  screw  hole  plug  using plug wrench (Figures 3.16b and 3.16c). FIGURE 3.16c. FIGURE 3.15a. FIGURE 3.16b. F-226