Removal and Installation of Unit Injectors on 3114, 3116, and 3126 MUI Engines{1251, 1290} Caterpillar

Introduction

This Special Instruction contains the necessary procedure in order to install unit injectors for 3114, 3116, and 3126 MUI engines.

Removal and Installation Procedure

Note: To avoid damage to the unit injector during removal of the unit injector from the cylinder head, refer to the Service Manual for the removal procedure of the unit injector.

Use the latest process for servicing the unit injector sleeves in the cylinder head before you install replacement unit injectors. Refer to the Service Manual and other service news articles in order to find the latest service information, including new tools and procedures.

Before a new unit injector or a remanufactured unit injector is installed into an engine, take adequate precautions in order to clean the internal fuel lines and the unit injector sleeve. Also, install a new AVSpare high efficiency fuel filter.

Lubricate the injector rack bar with clean diesel fuel or 1U-8265 Penetrating Oil .

Illustration 1	g02144296
Incorrect testing procedure for the tappet spring

Do not depress the tappet spring. Refer to Illustration 1. Do not force the injector rack bar in and out since this action may damage the internal parts of the unit injector. A tight rack on a unit injector that is not installed in the engine is not an indication of a faulty unit injector. Forcing the injector rack bar in and out may cause the unit injector to become damaged. Forcing the injector rack bar in and out may possibly void all the warranty.

Do not test the unit injectors prior to engine installation. The unit injectors are tested 100% at the factory and Pop Testing may contaminate the unit injector.

Before you install the unit injector, apply clean engine oil on the O-ring seals for ease of installation.

Install the unit injector according to the procedure in the Service Manual by using 173-1530 Injector Seating Tool . Tighten the unit injector clamp retaining bolt to a torque of 12 ± 3 N·m (9 ± 2 lb ft).

Verify the following parameters and settings according to the procedures in the Service Manual: unit injector synchronization, fuel setting, fuel timing and valve lash. Adjust the parameters and settings in order to meet specifications only.