Checking and repairing fuel injectors Checking fuel injectors Fig. 1 The nozzle tester (manual test stand) is used to check the opening pressure tightness spray pattern of the injection nozzle. Use pure testing oil or pure Diesel fuel for the test. Prior to testing, clean nozzle and check it for wear, see page 34. 1 Fig. 2 Check injector assembly. Connect the nozzle’s supply connection to the test unit’s pressure line. 8 7 Danger: The high opening pressure may lead to severe injuries. Do not place hands under the jet. Wear safety goggles. 6 5 4 1. Checking opening pressure: Switch on the pressure gauge and slowly press lever downwards until the nozzle emits a jet with a light grating noise.
Read opening pressure from the pressure gauge. In the event of a pressure deviation insert a differ- ent shim. If the pressure is too low, insert thicker shims, if it is too high, insert thinner shims Ж . The initial tension of the compression spring Е de- creases if a high number of operating hours has been clocked up. Consequently, the injection pressure drops slightly. When repairing injection nozzles, always set the opening pressure to the upper limit (+ 8 bar). 3 2 1 2 1 Seal 2 Nozzle tension nut 3 Injection nozzle 4 Intermediate washer 5 Pressure pin 6 Compression spring 7 Shim 8 Circlip Note: Shims are available in 0.05 mm steps from 1.0 mm to 1.98 mm. 2. Checking tightness:
Actuate hand lever. At a pressure of 20 bar below the opening pres- sure set not a single drop must fall from the nozzle opening within 10 sec. 3. Checking jet: Switch off pressure gauge and carry out some swift strokes. The nozzle must emit an audible grating noise and / or a well-atomised jet. Nozzles that satisfy these three requirements can be reused. 33