Edo; The cap and adjustment screw you are looking for are under the rear of injection pump, not readily visible on first look. Remove that bent looking plate next to pump to gain access and provide wrench swing. The cap is like a long acorn nut. When the "cap" is removed there will be a screwdriver bolt held in adjustment by a nut. Crack the nut lose so the screwdriver bolt can turn and procede from there. Use box end of wrench. You may find also a cable type "seal" on this adjustment that will probly need to be cut to do the adjustment. Good luck.