3126E On-highway Engine Caterpillar

Illustration 1	g00854956
(1) Unit Injector Hydraulic Pump (2) Oil Inlet Port (3) Fuel Transfer Pump (4) Drive Gear

Illustration 2	g00854591
(5) Fuel transfer pump bolt (6) Tie bolt (7) Oil outlet port (8) Fuel inlet port (9) Tie bolt (10) Fuel outlet port

Note: Weight of the unit injector hydraulic pump is approximately 29 kg (64 lb).

1. Attach a suitable lifting device to the unit injector hydraulic pump.

2. Position the unit injector hydraulic pump onto the engine. Install the mounting bolts into the pump housing and tighten the bolts.

3. Reconnect the fuel supply lines (8) and (10) to the fuel transfer pump.

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Illustration 3	g00893446

4. Use the following procedure to install the hydraulic hose assembly (12) to the unit injector hydraulic pump.

   1. Install the Snap To Connect (STC) fitting in the low pressure oil port (12) of the unit injector hydraulic pump.

   2. Align the Snap To Connect (STC) port connector (11) with the fitting that was installed in step 4.a.

   3. Push the connector onto the (STC) fitting until the connector snaps together. You should hear a definite snap and a solid stop should be felt.

   4. Abruptly pull back on the hydraulic hose assembly in order to verify that a proper connection has been made. The coupling should not separate.

5. Reconnect the high pressure oil line (7) to the unit injector hydraulic pump. Use the following sequence:

   1. Align threads of the connector assembly to the ports on the pump and head. Connect tube assemblies by hand prior to tightening with tools.

   2. Tighten the connector assembly to the ports 40 + 5 N·m (30 + 4 lb ft).

   3. Align the threads of the tube assembly to the connector assembly. Start tube connections before additional tightening with tools.

   4. Tighten the nuts to the connectors 40 + 4 N·m (30 + 3 lb ft).

6. Reconnect the sensor connector to the top of the unit injector hydraulic pump.

7. Replace the fuel filter.

8. Check the oil lines, fuel lines and the fuel pump for leakage.

End By: Install the air compressor. Refer to Disassembly and Assembly, "Air Compressor - Remove and Install".