3408 VEHICULAR ENGINE FOR 768C TRACTOR & 769C TRUCK Caterpillar


Automatic Timing Advance

Usage:

Remove Automatic Timing Advance

START BY:

a. remove fan drive and fan belt tightener

NOTE: The radiator guard assembly and fan were removed only for photographic purposes.

1. Remove fuel filter and base (1). Put protective covers in the fuel openings.

2. Remove support (2).

3. Remove the bolts and nut that hold cover (3) and the gasket to the engine front housing. Be sure to remove bolt (4) behind the front housing.

4. Set the fuel injection pump and flywheel on No. 1 TDC compression stroke. Use tools (A) and (B) to make this setting. See Remove Fuel Injection Pump Housing And Governor.

5. Remove four bolts (5) and retainer (6) from automatic timing advance (7). Remove automatic timing advance (7).

6. Do not let timing gear (8) come off the timing advance. Internal parts can fall inside the engine and ring (9) can break.

Install Automatic Timing Advance

1. Put automatic timing advance (1) in position in the front housing, and install the retainer and the bolts. Tighten the bolts finger tight until there is a small amount of friction (slight drag) between the retainer and the timing advance unit. This will prevent movement (backlash) when the gears are turned to the correct timing position.

2. Remove timing bolt (2), cover (3) and plug (4).

3. Use tool (A) to turn the engine in a counterclockwise direction (as seen from the flywheel end of the engine) until timing bolt (2) can be installed into the flywheel. The No. 1 piston must be at top center on the compression stroke.

NOTE: If the hole in the flywheel is turned beyond the hole in the flywheel housing, turn the flywheel back (clockwise) a minimum of 30° beyond the hole in the flywheel before turning counterclockwise toward the hole again. This will prevent a timing error caused by play in the timing gears.

4. To see if No. 1 piston is on the compression stroke, look at the valves of No. 1 cylinder. The valves will be closed if No. 1 cylinder is on the compression stroke. You should be able to move the rocker arms up and down with your hand.

If No. 1 piston is not on the compression stroke, turn the flywheel 360°, and install the timing bolt.

5. Remove the plug from the front of the fuel injection pump housing. Install tool (B) through the hole in the pump housing. If the timing is correct, tool (B) can be installed into the notch in the fuel injection pump camshaft.

6. If tool (B) cannot be installed into the notch of the camshaft, remove it and the timing bolt from the flywheel.

7. Repeat Step 3 and turn the flywheel an additional 360°. Repeat Step 4.

8. Tighten the bolts that hold the automatic timing advance to a torque of 25 N·m (18 lb.ft.); then tighten the bolts to a torque of 136 ± 7 N·m (100 ± 5 lb.ft.). Remove the timing bolt (2) from the flywheel.

9. Turn the engine two complete revolutions, and check the timing again. If tool (B) will not go into the notch of the fuel injection pump camshaft, do Steps 1 through 8 again.

10. If replacement of stud (7) is necessary, put 9S3263 Thread Lock on the threads of the new stud. Install it in the engine front housing until it is 73.2 mm (2.88 in.) above the outside surface of the front housing.

11. Put cover (6) and the gasket on the engine front housing, and install the bolts and nut that hold it. Be sure to install bolt (5) from the rear.

12. Install support (9) and fuel filter and base (8).

13. Remove the protective cover, and connect the fuel hoses. Connect the wiring.

END BY:

a. install fan drive and fan belt tightener

Disassemble Automatic Timing Advance

START BY:

a. remove automatic timing advance

1. Remove ring (1) and gear assembly (2) from the flange assembly.

2. Remove the slides from the weights.

3. Remove springs (4) and weights (3) from the flange assembly.

Assemble Automatic Timing Advance

1. Put weights (2) in position in flange assembly (1) as shown.

2. Install springs (3) in flange assembly (1).

3. If pistons (6) were removed from the gear assembly because of wear, use new parts for replacement. Install new pistons (6) until they are 11.05 ± 0.13 mm (.435 ± .005 in.) above the inside surface of gear assembly (4). Move the metal (peen) on the outside surface of gear assembly (4) in four places around each piston to hold them in position.

4. Use 1P808 General Purpose Lubricant to hold slides (5) in position on gear assembly (4).

5. Install gear assembly (4) on flange assembly (1). Make sure slides (5) fit in grooves of the weights.

6. Install the ring that holds gear assembly (4) to the flange assembly.

END BY:

a. install automatic timing advance

Caterpillar Information System:

3408 VEHICULAR ENGINE FOR 768C TRACTOR & 769C TRUCK Fuel Rack Travel
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