Bringing the piston of the first cylinder to the top dead center (TDC) position (Nissan Maxima A32)

1. Top dead center (TDC) is the highest point of the piston stroke in its cylinder. Strictly speaking, in 4-stroke engines, during the rotation of the crankshaft, this position is reached by each of the pistons twice: once at the end of the compression stroke and the second time at the end of the exhaust stroke. When adjusting the valve timing and setting the ignition timing angle, in the vast majority of cases, the TDC position of the end of the piston compression stroke is used (usually the first cylinder).

2. The need to bring the piston(s) to the TDC position arises when performing many procedures, in particular such as removing/installing camshafts and timing drive components.

3. Make sure the transmission is in neutral (position "P" on models with automatic transmission), then firmly set the parking brake or chock the rear wheels of the vehicle. Also immobilize the ignition system by disconnecting the connectors of the primary circuit wiring of the coils and removing the assemblies of the latter together with the spark plugs (see Chapter Settings and ongoing maintenance).

4. Bringing any of the pistons to the TDC position is done by turning the engine crankshaft in one of the ways described below. If you look at the engine from the front (from the drive belt side), the normal direction of rotation of the crankshaft is clockwise. Remember that attempting to turn the shaft counterclockwise may result in the timing belt being out of adjustment:

• a) The most effective method is to turn the shaft in the normal direction by means of a bolt screwed into the end of its front journal using a ratchet socket wrench;
• b) Using a remote starter switch will save time (follow the manufacturers instructions). As soon as the piston is close enough to TDC at the end of the compression stroke, the starter is stopped and further adjustment is carried out by the method described in point (a);
• c) If an assistant is available, the engine can be pre-cranked by short jerks from the driver's seat under the operator's guidance. The principle is the same as described in point (b). The final adjustment is again made manually, using a socket wrench (see point a).

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5. Install the compression tester into the spark plug hole of the first cylinder (see Part C of this Chapter - a compression tester with a threaded attachment should be used, and begin turning the crankshaft by the pulley bolt in the normal direction.



6. As the piston approaches the TDC position at the end of the compression stroke, the pressure in the cylinder will begin to increase, which is easily monitored by the compression gauge. Continue turning the shaft until the timing marks on the crankshaft pulley are aligned. If the TDC position is accidentally passed, turn the shaft two more full turns in the normal direction.