General information
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, each of the pistons reaches this position 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, in the vast majority of cases, the TDC position of the end of the piston compression stroke is used (usually the first cylinder).
The need to bring the piston (to her) TDC position occurs during many procedures, in particular, such as removing / installing camshafts, timing drive components and ignition distributor.
Some engines are designed in such a way that when crankshaft or camshaft is turned (s) shafts, with the timing belt/chain removed, the valves may come into contact with the piston crowns, risking damage to the related internal components, up to and including destruction of the cylinder head casting.
Do not change the position of the shafts after removing the belt!
How to perform the procedure
The layout of the alignment marks of the timing gears (1) and cranked (2) shafts in the TDC position of the end of the compression stroke of the piston of the first cylinder
Bringing any of the pistons to the TDC position is done by turning the crankshaft of the engine. When looking at the engine from the timing end, the normal direction of rotation of the crankshaft is clockwise. Remember that an attempt to turn the shaft counterclockwise can lead to a violation of the valve timing adjustments. The first is the cylinder, extreme from the side of the timing drive.
1. Disconnect the negative battery cable. Remove all spark plugs to make engine cranking easier.
2. In order to provide access to the TDC mark on the camshaft gear, remove the timing cover (see Removing and installing timing cover).
3. Using a wrench put on the crankshaft pulley bolt, turn the latter in the direction of normal rotation until the timing mark of the camshaft gear is aligned with the counter risk on the top of the back cover of the timing belt. The mark on the rim of the gear wheel of the crankshaft must be aligned with the mark on the oil pump housing (see illustration The layout of the alignment marks of the timing gears (1) and cranked (2) shafts in the TDC position of the end of the compression stroke of the piston of the first cylinder).
When the above conditions are met, the engine will be brought to the TDC position of the end of the compression stroke of the piston of the first cylinder.
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