Chapter 18 Injection Nozzles 383 Copyright Goodheart-Willcox Co., Inc. Opening Pressure Close the pressure gauge valve and flush the nozzle by operating the test pump rapidly. Open the gauge valve and raise the pressure slowly until the nozzle valve opens. The gauge reading will drop sharply at this point. Check opening pressure against service manual specifications. Note: Capped pencil nozzles are tested in the same manner except the cap must be removed. If the opening pressure is incorrect, remove the nozzle from the test pump and mount in a holding fix- ture. Loosen the adjusting screw locknut, Figure 18-32, and reconnect the nozzle to the tester with the tip facing downward. Loosen the lift adjusting screw two or three turns to prevent interference while adjusting the opening pressure. Turn the pressure adjusting screw clockwise to increase or counterclockwise to decrease the opening pressure, Figure 18-33. After setting to specifications, remove the nozzle from the tester and secure it in the holding fixture, tightening the adjusting screw locknut to specifications, Figure 18-34. Valve Lift Reconnect the nozzle to the tester. Pump fuel through the nozzle and slowly turn the lift adjusting screw clockwise until the valve ceases to open. Do not manually bottom the valve with excessive force as bending may result. Check for bottoming by raising pressure to 200–500 psi (1379–3448 kPa) above nozzle opening pressure. Although some fuel may collect at the top, a rapid dribble should not be apparent. Now turn the lift screw counterclockwise the amount indicated on the individual nozzle specification sheet. Recheck opening pressure. After adjustment is made, the locknut must be torqued to specifications. Note: Lift is always set before checking spray pattern and chatter as the amount of lift will affect these characteristics. Carbon dam seal Figure 18-31. Removing the carbon dam seal using a knife. (Stanadyne Diesel Systems) Vise Nozzle Holding fixture Figure 18-32. Loosening adjusting screw locknut with nozzle in holding fixture. (Stanadyne Diesel Systems) Lift adjusting screw Figure 18-33. Adjusting the opening pressure by turning the lift adjusting screw. (Stanadyne Diesel Systems) Nozzle Torque wrench Adapter Figure 18-34. Torquing the pressure adjusting screw locknut. (Stanadyne Diesel Systems)