ADJUSTMENT AND CLEANING OF 9N3979 FUEL
NOTE: Do not clean or adjust a nozzle with a valve
opening pressure (VOP) less than 1500 psi (10300 k
Valve Opening Pressure (VOP) Adjustment
FUEL INJECTION NOZZLE
1. Fuel injection nozzle. 2. Locknut (for pressure
adjustment screw). 3. Pressure adjustment screw.
4. 1H1023 O-ring Seal for cap. 5. Locknut (for lift
adjustment screw). 6. Lift adjustment screw.
1. Remove fuel injection nozzle (1) from the 5P4150
Nozzle Tester and put it in the 8S2250 Nozzle
Holding Tool (P).
1. Fuel Injection nozzle. 7. 8H8502 Combination
Wrench. P. 8S2250 Nozzle Holding Tool.
2. Loosen locknut (5) that holds lift adjustment screw
(6). Turn lift adjustment screw (6) counterclockwise
If the lift adjustment screw is not turned
counterclockwise two turns, the valve can be
bent or the seat for the valve can be damaged
when the pressure adjustment screw Is turned.
3. Hold lift adjustment screw (6) with a 5/64" hex
wrench (8) and remove locknut (5).
5. Locknut (for lift adjustment screw). 8. 5/64" hex
1. Fuel Injection nozzle. 9. 8H8505 Combination
4. Loosen locknut (2) that holds pressure adjustment
5. Put fuel injection nozzle (1) on the nozzle tester.
Turn pressure adjustment screw (3) clockwise with
5P4813 Socket (10). Each one-fourth of a turn will
increase the opening pressure approximately 250
psi (1720 kPa).