Testing and Inspection of Injection Nozzle
Fuel Injector: Testing and Inspection
Injection Nozzle
NOZZLE TESTING
1.
Install nozzle into a suitable nozzle tester and bleed air from union nut. Do not place fingers over nozzle injection orifice.
2.
Gradually pump tester handle several times to discharge any carbon build-up from injection orifice.
3.
Pump tester handle slowly and note pressure gauge reading. Read pressure gauge when injection pressure begins to drop. Nozzle opening pressure
for a used nozzle should be 1707-2389 psi on 1984 models or 2276-2389 psi on 1985 models.
Fig. 23 Adjusting shim thickness chart
4.
If nozzle opening pressure is not within specifications, disassemble nozzle as described previously and change adjusting shim on top of nozzle
pressure spring. Shims are available in different sizes as shown in Fig. 23. Varying adjusting shim thickness by .0020 inch (.05 mm) will
change injection pressure by approximately 91 psi.
5.
While maintaining pressure at approximately 142-284 psi, ensure that there is no fuel drip for 10 seconds from injection orifice or retaining nut.
Fig. 24 Checking nozzle spray pattern
SPRAY PATTERN TEST
1.
The fuel injection nozzle should shudder at a pumping speed between 15-60 times per minute for a used nozzle or 30-60 times per minute for a
new nozzle.
2.
Check spray pattern during shuddering, Fig. 24. If spray pattern is not correct, replace spray nozzle(s).