SETSCREW-SOCKET 3904226 - Caterpillar

Illustration 1. Location of 3408 Industrial (67U), Marine (99U), and Generator Set (78Z) Engine fuel line group components.
Illustration 2. Location of 3412 Industrial (38S), Marine (60M, 7HG), and Generator Set (81Z, 5AG) Engine fuel injection line group components. New wider [19.0 mm (.75 in) versus 12.0 (.47 in) fuel line clamp assemblies are used on 3412 engines. See Illustration 2 and Chart F for the locations and identification of 4P3677, 4P3678, 7C6591, and 7C7747 Clamps. The wider clamps are required for additional fuel line support.
Illustration 3. Location of Undercut Hex (A) and Collar (B) on the new fuel lines.
Illustration 4. Section B-B. Components of 6I4813 Clamp Kit. (31) 1022731 Spacer Bar. (32) 6I4811 Damper. (33) 6I4812 Clamp. (34) 7M2931 Screw. (35) 6D3848 Washer.A new formed viton damper clamp (3412 ONLY) is used on the fuel line assemblies for the number 4 and 6 cylinders. See Illustration 2 (Section B-B) for the location and Illustration 4 for the new clamp component identification.
Illustration 5. Section C-C. Location of new shorter clamp components for the Number 2 fuel line. (36) 9Y3357 Clamp. (37) 1029228 Clamp. (38) 5P4939 Screw.Also on all 3412 Engines, a new clamp assembly is used on the Number 2 fuel line assembly (4P7802). The new clamp assembly is shorter and provides more effective support than the former long clamp assembly. See Illustration 2 (Section C-C) for the location and Illustration 5 for the new clamp component identification.
For Non-Aftercooled Engines
New fuel line support brackets are used on engines that do not include aftercoolers. On 3408 engines these are the 4P8261 and 4P8385 Brackets. On 3412 engines this is the 6I0348 Bracket Assembly.
All 3408 And 3412 Engines
Before removing any clamps, mark their location with tape or some other non-damaging method. This will help insure that the clamps are reinstalled in the correct locations. Use a 6V6069 Torque Screwdriver or similar tool to tighten the clamp screws to a torque of 2.25 N m (20 lb in).
Do not force fuel injection line ends into position and then begin to tighten the nuts on the ends of the lines. The result will be added strain on the lines. If needed, gently bend the lines by hand until the lines are the correct shape for the nuts to be easily started. Before tightening the nuts on the ends of the fuel injection lines, use the fuel priming pump to purge air from the fuel system. Tighten the fuel injection line nuts to a torque of 40 7 N m (30 5 lb ft). After starting the engine and checking for leaks, tighten the fuel injection line nuts again to a torque of 40 7 N m (30 5 lb ft).