Chapter 18 Injection Nozzles 375 Copyright Goodheart-Willcox Co., Inc. ❑ Replace the fuel filter(s). ❑ Check the air supply to the engine. ❑ Check the injection pump timing, adjusting to specifications, if needed. ❑ Check for proper engine speed, adjusting to spec- ifications, if needed. ❑ Check for proper injector advance (if applicable). If the problem is not isolated or corrected after completing these steps, the nozzles should then be checked. To locate a faulty injector that may be causing incomplete combustion, misfiring, rough running, or excessive smoke emission, start the engine and check for leaking high pressure connections. When the engine reaches operating temperature, accurately determine engine low idle speed using a tachometer. Warning: The following procedure involves opening high pressure fuel lines during engine operation. Always wear safety gog- gles and position rags over the connection to catch the fuel stream. Crack open the individual fuel injection lines at the injector, one at a time. As each line is cracked open, listen for any change in engine idle. A faulty injector will not have as great an effect on engine idle as the other injectors. Warning: This procedure can only be per- formed on hydraulic injectors and never on common rail systems because they operate under extremely high pressures. Injector Removal Cleanliness cannot be overstressed when servicing the fuel injection system. Before removing the injector from the engine, clean the surrounding area. When possible, use compressed air to blow dirt and dust away from the injectors. Be sure to wear safety glasses while using any compressed air. Make sure all lines and connections are absolutely clean before removing the injector. Note: The following injector removal and service procedures are typical for many systems. Each injector manufacturer pro- vides specialized tools and procedures for servicing their injectors. Always consult the proper shop manual before servicing injector holders or nozzles. Disconnect the high pressure lines from the injector nozzles, Figure 18-11A. Immediately cap all disconnected fuel lines to prevent dirt from entering the system, Figure 18-11B. If the injector is held by a flange, remove the hold-down cap screw or the nuts from the stud bolts, Figure 18-12. If the injector is held by a clamp, remove the cap screw and slide the clamp out of the injector groove. If necessary, twist the nozzle holder with a wrench placed on the holder flats to help loosen the copper sealing gasket at the bottom of the nozzle. Using an injector pry bar, pry the injector straight up out of its bore, Figure 18-13. Be extremely careful not to Remove injection line nuts at nozzle Install plastic caps to protect injection lines A B Figure 18-11. A—Removing injection line nuts at the nozzles. B—Capping the injection lines to prevent dirt from entering the fuel system. (Navistar International Transportation Corp.) Clamp (crab) & bolt Figure 18-12. Removing nozzle hold-down clamps. (Navistar International Transportation Corp.)