3114, 3116 and 3126 Engines Caterpillar

Unit Injector

Usage:

This procedure is an inspection of the unit injectors and the rocker arm assemblies.

Without removing any injectors, inspect the injectors for seizures and for cracked springs or broken springs. A seized injector can be identified by a compressed spring and a loose rocker arm. Replace seized injectors. Check for bent push rods or rocker arms. Replace damaged parts with new parts, as needed. Replace injectors that have broken springs or cracked springs. Ream the injector sleeve if the seat area for the injector is pitted. Replace the injector sleeve, if necessary. Refer to Tool Operating Manual, NEHS0738, "Using the Injector Seating Tool " and Tool Operating Manual, NEHS0610, "Using the 128-8822 Tool Group on 3114, 3116, and 3126 Engines with Mechanical Unit Injectors (MUI)" for additional information about replacing injectors. Also, refer to Video Tape, LEVN4032, "Troubleshooting Guide for the 3100 Family of Diesel Engines" and Video Tape, LEVN4732, "Injector Seating Procedure". Verify synchronization and timing after an injector is reinstalled or an injector is replaced.

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Check the rocker arms and the rocker arm bolts for cracks, wear, or damage. Tighten the rocker arm bolts evenly to a torque of 33 ± 7 N·m (24 ± 5 lb ft).

Check the contact between the rocker arm and the injector. If follower (1) for the rocker arm is missing, replace the follower. Ensure that thrust plate (2) is in position on top of the injector. If the thrust plate is not found, check the valve compartment. If the thrust plate is located and the thrust plate is undamaged, reinstall the thrust plate. Use a new O-ring if the thrust plate is reinstalled. Replace the injector if the thrust plate is not found. Also replace the injector if the thrust plate is found but the thrust plate is damaged.

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Illustration 2	g00615272
(3) Fuel injection rack (4) Cone (5) O-ring


NOTICE
Do not remove the fuel control linkage or the fuel injection racks without having the spring compressors installed. Damage to the injectors may occur.

Ensure that all of the hold down bolts for the injectors are tightened to a torque of 12 ± 3 N·m (106 ± 27 lb in). If an incorrectly tightened bolt is found, remove the injector that is held down by the bolt. Examine the sealing surface for the injector sleeve. Ream the injector sleeve if the seat area for the injector is pitted. Replace the injector sleeve, if necessary. Replace the injector only if injector cone (4) is damaged. A burned O-ring or a missing O-ring on the end of the injector does not indicate a faulty seal. The O-ring does not need to be replaced. Verify synchronization and timing after an injector is reinstalled or an injector is replaced. Refer to the System Operations, Testing And Adjusting module.