3412E Petroleum Engine Finding Top Center Position for No. 1 Piston Caterpillar

The No. 1 piston at Top Center (TC) on the compression stroke is the starting point of all timing procedures.

Note: Some engines have two threaded holes in the flywheel. These holes are in alignment with the holes with plugs in the left and right front of the flywheel housing. The two holes in the flywheel are at a different distance from the center of the flywheel so the timing bolt cannot be put in the wrong hole.

Illustration 1	g00841434
Locating the top center position (typical example) (1) Timing bolt location (2) Plug (3) Bolt (4) Cover

1. Remove the timing bolt (1), the bolt (3) and the cover (4) .

2. Remove the plug (2) .

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Illustration 2	g00841440
Using 9S-9082 Engine Turning Tool (1) Timing bolt (5) 9S-9082 Engine Turning Tool

4. Install the 9S-9082 Engine Turning Tool (5) in the housing. The 9S-9082 Engine Turning Tool and an appropriate wrench should be used in order to turn the engine flywheel in the direction of normal engine rotation. Normal engine rotation is counterclockwise. Normal engine rotation is viewed from the flywheel end of the engine.

5. Once plug (2) has been removed, insert the timing bolt (1) through the hole. Hold the timing bolt (1) against the flywheel.

6. Turn the flywheel in the direction of normal engine rotation until the timing bolt engages with the threaded hole. The No. 1 piston is at the top center position on the engine.

   Note: If the flywheel is turned beyond the point of engagement, the flywheel must be turned in the opposite direction of normal engine rotation approximately 30 degrees. Then turn the flywheel in the direction of normal rotation until the timing bolt engages with the threaded hole. The procedure will eliminate the backlash that will occur when the No. 1 piston is put on the top center.

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Illustration 3	g00841480
Cylinder and valve locations for 3412E engines (A) Inlet (B) Exhaust

7. Remove the left front valve cover. Look at the valves of No. 1 cylinder. The valves will be closed if the No. 1 piston is on the compression stroke. You can move rocker arms up and down with your hand. If the No. 1 piston is not on the compression stroke, perform the following steps.

8. Remove the timing bolt from the flywheel.

9. Rotate the crankshaft counterclockwise by 360 degrees. Install the timing bolt.

Note: If the flywheel is turned beyond the point of engagement, the flywheel must be turned in the opposite direction of normal engine rotation approximately 30 degrees. Then turn the flywheel in the direction of normal rotation until the timing bolt engages with the threaded hole. The procedure will eliminate the backlash that will occur when the No. 1 piston is put on the top center.