Chapter 18 Injection Nozzles 379 Copyright Goodheart-Willcox Co., Inc. Check the valve seat for wear and replace the nozzle assembly if the seat is excessively worn. Slight irregulari- ties in the seat can be corrected by regrinding using special tools. Injector rebuilding is normally performed in a fully equipped specialty shop. Clean the outside of the nozzle body with a soft brass brush and check for discoloration and damage to the pres- sure face and spray holes. The pressure surface of the body that contacts the holder must be clean and free of scratches. The surface of the nozzle body can be lapped using a fine compound such as jeweler’s rouge and a lapping plate or block. Use a figure eight pattern when lapping any injector nozzle part, Figure 18-21. Rinse the nozzle body in clean diesel fuel and inspect the lapped surface for smoothness. A small diameter drill bit or wire can be used to clean the internal fuel duct, Figure 18-22. Special reaming tools are available for cleaning carbon deposits from cavities and bores. These tools will vary between injector manufacturers. Insert the tool and rotate it to clear out the carbon. Hard or sharp tools, emery cloth, grinding compounds, or other abrasives must not be used to clean nozzle tips. The pintle nozzle orifice can be cleaned with a toothpick. The small holes in the tip of a hole nozzle can be cleaned by probing them with a cleaning wire held in a pin vise or a spe- cial tool designed for the job, Figure 18-23. The cleaning wire should be slightly smaller than the size of the hole in the tip, Figure 18-24. Care must be exercised in cleaning these holes to prevent the wire from breaking in the hole. If this happens, the broken pieces may be impossible to remove. One of the better nozzle tip cleaning methods is to use a nozzle-flushing device. The nozzle mounts in the cleaner stand and a special cleaning oil is pumped through the nozzle openings to dis- solve and remove the carbon deposits. Reassembly Scrape all loose carbon from the nozzle retaining nut and check for cracks and damaged threads. Clean the sealing surface of the retaining nut using a brass brush. Thoroughly rinse the valve and nozzle body in clean test oil before reassembly and testing. If the inlet fitting was replaced, tighten it to the recommended torque and flush the holder body to remove any metal chips. Assemble any required spacers and insert them into the holder body spring bore. Insert the adjusting spring and spring seat into the spring bore. Figure 18-24. Be careful when cleaning nozzle spray orifices. If you break the pin in the nozzle, it may be impossible to recover the broken piece. (Kuboda) Figure 18-21. When lapping an injector nozzle part, it should be moved lightly over the surface of the lapping block in a figure eight pattern. (Detroit Diesel Corporation) Small drill Fuel feed channel Nozzle body Figure 18-22. Cleaning the fuel feed channel using a small diameter drill bit. Pin vice Figure 18-23. Cleaning spray tip orifices with a special tool. (Detroit Diesel Corporation)