2000/02/01 Caterpillar

Truck Engines:

3126 (S/N: 1WM; 4ES; 8HW; 1BW; 6RW; 7LZ)

Description of Change: A new injector hydraulic pump lines group is being used in the HEUI Fuel System on these truck engines. This new group has an improved tube design. The new tube has a stainless steel orifice that is pressed into the tube. There is not an orifice in the fitting in the high pressure oil manifold. The previous design used an orificed fitting in the high pressure oil manifold and a tube that did not have an orifice.

Adaptable To: The new 172-6296 Injector Hydraulic Pump Lines (Group) has replaced the 105-1792 Injector Hydraulic Pump Lines (Group) in production. Neither group is serviced at the group level. Refer to the following illustrations and tables in order to identify the components of the new 172-6296 Injector Hydraulic Pump Lines (Group) and the previous 105-1792 Injector Hydraulic Pump Lines (Group).

Illustration 1	g00672630
Illustration of the new 172-6296 Injector Hydraulic Pump Lines (Group)

Table 1

Components of the New 172-6296 Injector Hydraulic Pump Lines (Group)
Item	Qty	Part Number	Description
1	1	135-5973	Injector Clamp
2	1	107-7808	Washer
3	1	8T-0292	Bolt
4	1	9M-1974	Hard Washer
5	2	125-3296	Bolt
6	1	164-0201	Tube
7	1	148-0876	Fitting
8	1	033-5853	O-Ring Seal
9	1	113-6303	O-Ring Seal
10	1	113-6091	Seat

Illustration 2	g00678892
Illustration of the previous 105-1792 Injector Hydraulic Pump Lines (Group)

Table 2

Components of the Previous 105-1792 Injector Hydraulic Pump Lines (Group)
Item	Qty	Part Number	Description
1	1	135-5980	Injector Clamp
2	1	107-7808	Washer
3	1	8T-0292	Bolt
4	1	9M-1974	Hard Washer
5	2	125-3296	Bolt
6	1	135-5980	Tube
7	1	113-6135	Fitting
8	1	033-5853	O-Ring Seal
9	1	113-6303	O-Ring Seal
10	1	113-6091	Seat

The HEUI fuel system requires one and ONLY one orifice in order to provide fluid stability. When the tube is installed on the engine, be certain that there is an orifice in either the tube or the fitting in the high pressure oil manifold. There should not be orifices in both the tube and the fitting in the high pressure oil manifold. The 125-3296 Bolt (1) that is used in this assembly can be used as a gauge. The bolt should fit into either the tube or the bolt should fit into the fitting in the high pressure oil manifold. The bolt should not fit into both the tube and into the fitting in the high pressure oil manifold. To ensure a proper combination, perform the following procedure:

1. Try to insert the bolt into the tube and into the fitting in the high pressure oil manifold.

2. If the bolt will fit into the tube and the bolt will fit into the fitting in the high pressure oil manifold, then no orifice is installed. This is not the correct combination of parts. There should be an orifice in either the tube or in the fitting in the high pressure oil manifold.

3. If the bolt will not fit into the tube and the bolt will not fit into the fitting in the high pressure oil manifold, then two orifices are installed. This is not the correct combination of parts. There should not be orifices in both the tube and the fitting in the high pressure oil manifold.

4. If the bolt will not fit into the tube but the bolt will fit into the fitting in the high pressure oil manifold, then an orifice is installed in the tube. This is a correct combination of parts.

5. If the bolt will not fit into the fitting in the high pressure oil manifold but the bolt will fit into the tube, then an orifice is installed in the fitting in the high pressure oil manifold. This is a correct combination of parts.

Determine that you have the correct combination of parts. Use the following procedure in order to install the injector hydraulic pump lines. Refer to illustration 7 and illustration 1. The procedure is the same for the new 172-6296 Injector Hydraulic Pump Lines (Group) and the previous 105-1792 Injector Hydraulic Pump Lines (Group).

1. Install fitting (7) and seal (8) in the high pressure oil manifold. Tighten fitting (7) to a torque of 25 N·m (18 lb ft).

2. Position O-Ring seal (9) and seat (10) on the center of the top of the fuel injector.

3. Install the end of the tube (6) with the flare nut on the fitting in the high pressure oil manifold and install the other end of the tube on the fuel injector. Thread the flare nut on tube (6) into the high pressure oil manifold. Tighten the flare nut until the flare nut is hand tight. Tube (6) should be seated on the flare of fitting (7) .

4. Install bolts (5) through the flange on tube (6). Thread the bolts (5) into the fuel injector. Tighten bolts (5) evenly. Tighten bolts (5) until the bolts are hand tight.

5. Install clamp (1) with bolt (3) and washers (2) and (4). Tighten bolt (3) to a torque of 30 N·m (22 lb ft).

6. Tighten the flare nut on tube (6) at the high pressure oil manifold to a torque of 40 N·m (30 lb ft).

7. Tighten bolts (5) to a torque of 3 N·m (27 lb in).

8. Tighten bolts (5) again. Tighten bolts (5) to a torque of 5 N·m (44 lb in).