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) to the TDC position occurs during many procedures, in particular, such as removing / installing camshafts, timing drive components and an ignition distributor.
Some engines are designed in such a way that when crankshaft or camshaft is turned (s) shafts, when the timing belt is removed, the valves can come into contact with the piston crowns, which is fraught with the risk of damage to the corresponding internal components, up to the destruction of the cylinder head casting.
Do not change the position of the shafts after removing the belt!
How to perform the procedure
1. Bringing any of the pistons to the TDC position is done by turning the engine crankshaft. 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 extreme cylinder on the timing drive side.
2. Disconnect the negative battery cable. Remove all spark plugs to make engine cranking easier.
3. In order to provide access to the TDC mark on the camshaft gear, remove the top cover of the timing drive (see Section Removing and installing timing cover).
4. Turn the crankshaft clockwise so that the camshaft cams that control the valves of the first cylinder are facing the tapered part up.
5. You can turn the crankshaft by rotating the front wheel with the 5th gear installed, or by rotating the crankshaft itself by the central bolt securing its pulley with the manual transmission or AT in the neutral position and the parking brake cocked.
Do not turn the engine over the camshaft gear bolt, as this can overload the toothed belt.
6. Align the mark on the camshaft sprocket with the TDC mark on the timing belt cover. In this case, the mark on the crankshaft pulley (C14NZ engine) must match the mark on the lower timing belt cover. On engines X12SZ and C14SE the mark is on the crankshaft gear. In this case, the piston of the first cylinder is in the TDC position.
Setting marks TDC engine C14NZ
TDC alignment marks for X12SZ and C14SE engines
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