Fuel Injector: Service and Repair
INJECTION NOZZLE
WARNING: Wipe up any spilled fuel because it can cause a fire.
CAUTION:
- Be sure not to touch the slide-contact area of needle valve 10 because any scratches or corrosion might spoil the airtightness of nozzle 11. It must be handled with utmost care.
- Never change the combination of needle valve 10 and nozzle 11 for each cylinder.
- Be sure to protect all openings by covering them after removal of hoses and pipes because the engine performance is adversely affected if dirt and foreign particles enter injection nozzle assembly 6.
NOTE: Remove carbon deposits and clean injection nozzle assembly 6 before working on it, then test the injection pressure and jet spray condition, and check for fuel leakage before disassembly. If no fault is found, do not disassemble.
Service standards
Tightening torque
Special tools
Service procedure
- Inspection before disassembly
Attach injection nozzle assembly 6 to nozzle tester A, and conduct the following inspection.
WARNING: Never touch the spray from nozzle 11 or let your hands get too close to the spray point during the test.
NOTE: Before inspection, bleed the air out in a couple of bursts by pressing nozzle tester A lever.
1. Valve opening pressure
- Raise the pressure of nozzle tester A by operating the lever, and measure the pressure that the gauge registers when the pressure is released which will be observed by the sudden movement of the gauge indicator.
- If the measured value deviates from the standard value, disassemble the nozzle and clean, and adjust it using adjusting shims 14.
- Variation of 0.05 mm {0.0020 in.} thickness in adjusting shims 14 causes a difference of 735 kPa {105 lbf/in2, 7.5 kqf/cm2} of pressure, for example, to alter the pressure for 98 kPa {14 lbf/in2, 1 kqf/cm2}, a thickness of 0.0067 mm {0.00026 in.} is required.
- If the performance cannot reach the standard value even after adjustment, replace injection nozzle assembly 6.
2. Spray condition
- Test injection spray condition by quick lever actions of nozzle tester
A: 4 to 6 actions per second
A: Even spray from all five orifices (Good)
B: Even and symmetrical spray (Good)
C: Asymmetrical spray (Faulty)
D: Spray direction deviates from the nozzle axis line (Faulty)
E: Thin and insufficient spray (Faulty)
F: Irregular spray (Faulty)
- If faulty spray cannot be corrected, disassemble injection nozzle assembly 6 and clean every part and repeat the test. If faulty spray still occurs after repeating test, replace the injection nozzle assembly.
- Make sure that there is no post-spray dripping after injection.
3. Fuel air tightness and leakage at related contact points
- Maintain interior pressure of nozzle at 1960 kPa {285 lbf/in2, 20 kgf/cm2 } lower than the valve opening pressure, and check and see if any fuel seeps out of the nozzle tip within 10 seconds.
- If any fault is found, disassemble injection nozzle assembly 6 and clean every part and repeat the test. If any fault is still found, replace the injection nozzle assembly.
[6] Injection nozzle assembly
[Disassembly]
CAUTION:
- Be sure not to touch sliding part A of needle valve 10 with your hands.
- Never change the combination of removed needle valve 10 and nozzle 11 for each cylinder.
[Cleaning]
Clean needle valve 10 and nozzle 11 with gas oil (cleaning solvent).
Remove carbon deposits with cleaning tool in the following manner:
- Clean needle valve 10 by removing carbon deposits from its tip using cleaning bar B of cleaning tool.
CAUTION: Never use a wire brush or hard steel for cleaning.
- To clean nozzle 11, remove carbon deposits from the orifices of the nozzle using needle cleaner C of cleaning tool, by inserting it into the orifices and turning it.
Needle cleaner diameter: 00.25 mm {0.0098 in.} or less
- Clean the seat of nozzle 11 using cleaning needle D of cleaning tool.
- Use FUSO carbon remover to remove hard-to-remove, burnt-on carbon deposits.
[Inspection]
- Immerse needle valve 10 and nozzle 11 in gas oil (cleaning solvent) and clean them thoroughly.
- Check and see if needle value 10 drops by its own weight into the nozzle from the position where a third of its length is pulled out. (Repeat this several times rotating the needle valve.)
- If needle valve 10 does not drop smoothly, repeat cleaning and repeat the test. If any fault is still found, replace both the needle valve and nozzle 11 together as a set.