376 Diesel Engine Technology Copyright Goodheart-Willcox Co., Inc. bend the nozzle holder and make sure the nozzle sealing washers come out with the nozzles. If the gaskets stick in the bore, remove them with an O-ring pick, Figure 18-14. With the injector removed, cap the fuel connection and wrap the nozzle in shop rags to protect it from damage. Cover the cylinder head opening. Caution: Do not use a screwdriver to remove an injector. Injector Testing Visually inspect the injector to determine if it requires simple cleaning and adjustment or more extensive ser vicing. If the spray tip, nozzle, or nozzle holder is discolored, corroded, or damaged, more extensive serving will prob- ably be required and the unit should be sent to a qualified fuel injection shop. If the injector appears to be in good shape, clean any external deposits from the nozzle and nozzle holder using a fine-wire brass brush, Figure 18-15, and then test injector operation using an injector tester. Pretesting of injectors before disassembly will confirm faulty operation. Warning: When installing an injector in the tester, position it so that the high-pressure injection spray cannot injure you or others, Figure 18-16. The high pressure of the injected fuel can easily puncture human skin. Follow the injector tester manufacturer’s mounting and operating instructions for all tests. Valve Open and Close Pressure Test To test the valve opening pressure and closing pressure, first close the tester’s pressure gauge valve and Insert pry bar in groove below nozzle holder flat and lift Figure 18-13. Prying the nozzle straight up out of its bore. (Navistar International Transportation Corp.) Copper gasket O-ring pick Nozzle bore Figure 18-14. Removing the copper sealing gasket from the injector bore using an O-ring pick. (Navistar International Transportation Corp.) Brass wire brush Figure 18-15. Clean the exterior surface of the injection nozzle with a fine-wire brass brush. The soft metal, brass, will not damage the surface. (Stanadyne Diesel Systems) Figure 18-16. Injector mounted in “pop” tester. Always direct the fuel stream into a suitable container. (Mack Trucks, Inc.)