Injection Nozzle Pressure

1. Install a suitable nozzle hand tester onto injection nozzle, then bleed air from nozzle by loosening nozzle union nut. Do not place fingers over nozzle injection orifice.
2. Pump tester handle a few times to discharge any carbon build-up from injection nozzle orifice.
3. Gradually pump tester handle and note tester gauge reading. Read pressure gauge reading when injection pressure begins to drop.
4. Opening pressure for a used nozzle should be 1920-2205 psi. Opening pressure for a new nozzle should be 2062-2205 psi. Proper nozzle operation can be determined by a swishing sound.
5. If nozzle opening pressure is incorrect an adjustment shim must be installed at the top of the pressure spring. Shims are available in different sizes in .0010 inch (.025 mm) increments. Varying adjusting shim thickness by .0010 inch (.025 mm) will change injection pressure by approximately 50 psi.
6. Perform leakage test as follows:
a. While maintaining pressure at 142-283 psi below opening pressure, ensure that there is no fuel drip for approximately 10 seconds from injection orifice or around retaining nut.
b. If nozzle drips fuel within 10 seconds, clean or replace nozzle as required.
7. Perform spray pattern test as follows:
a. Injection nozzle should shudder at a predetermined pumping speed between 15-60 times per minute on used nozzles or 30-60 times per minute for new nozzles.

Fig. 23 Nozzle spray pattern:

b. Check fuel spray pattern during shuddering period, Fig. 23.
c. If fuel spray pattern is incorrect during shuddering period, replace nozzle as required.