Note: The following procedure assumes that the distributor is installed correctly. If you need to set TDC to install the distributor, the piston position can be determined by plugging the spark plug hole of cylinder No. 1 with your finger, based on the change in pressure in the cylinder. Then you can set the TDC more accurately using the marks on the crankshaft pulley.
1. Top dead center (TDC) is the extreme upper position of the piston in the cylinder, which it can occupy when the crankshaft rotates. In a four-stroke engine, each piston is at TDC twice during the working cycle - at the end of the compression stroke and at the end of the exhaust stroke. Usually it has the value of TDC in the compression stroke,
2. Installation of pistons in the VMT is necessary when performing many repair and adjustment works, such as removal and installation of parts of the valve timing and ignition mechanism.
3. Before starting this operation, put the transmission in neutral and block the rear wheels, for example by applying the handbrake. Also disable the ignition system by disconnecting the low voltage wires from the ignition coil (see chapter 5). Also remove the spark plugs (see chapter 1) and turn off the fuel supply system (see chapter 4).
4. To set any piston to TDC, it is necessary to turn the crankshaft in one of the following ways. The normal direction of rotation of the crankshaft is clockwise when looking at the engine from the pulley side.
- a) The most common method of rotating the shaft is with a socket wrench placed on an end bolt screwed into the nose of the crankshaft.
- b) You can use a remote starter switch. If you have such a switch, use it according to the manufacturer's instructions. Bring the crankshaft close to the TDC position, then tighten it with a wrench as described above.
- b) You can ask an assistant to turn on the starter with the ignition key using short pulses. This method allows you to check the crankshaft fairly close to TDC, then tighten it further using method (a). Make sure your assistant removes the ignition key and exits the car.
Models produced in 1997 and earlier
5. Locate the terminal on the distributor cap. corresponding to cylinder #1. If the terminals on the cap are not marked, trace the high-voltage wire from the spark plug to the cap.
6. Mark the distributor cap and housing opposite terminal No. 1 with a felt-tip pen or chalk.
7. Remove the distributor cap and set it aside (if necessary see chapter 1).
8. Rotate the crankshaft until the notch on its pulley aligns with the TDC mark on the timing scale (figure 3.8).
9. Look at the ignition gel distributor rotor. It should be directed exactly at the mark you made on the body.
10. If the rotor is turned 180° relative to the mark, this means that piston No. 1, although at TDC, is finishing the exhaust stroke.
11. To bring piston No. 1 to TDC on the 8th compression stroke, turn the crankshaft a full revolution (360°) clockwise. Now the distributor rotor should turn towards the mark. If the distributor rotor points to the terminal of spark plug No. 1, and the mark on the crankshaft pulley coincides with the pointer. this means that piston No. 1 is at TDC in the compression stroke.
Note: If the distributor rotor is pointing towards spark plug contact #1 and the marks on the crankshaft pulley do not align, the camshaft drive belt is not installed correctly.
Models produced since 1998
12. Models produced since 1998 are equipped with a distributorless ignition system (see chapter 5). To set piston No. 1 to TDC, remove the spark plug from cylinder No. 1 and screw a compression gauge into the spark plug hole.
13. Turn the crankshaft (see point 4 of this paragraph). As the piston approaches TDC in the compression stroke, the pressure recorded by the compression gauge will begin to increase. Continue turning the crankshaft until the pointer on the crankshaft pulley aligns with the TDC mark (see figure 3.8). Once the pressure has started to increase, do not turn the crankshaft more than necessary to align the marks.
14. It may take up to two full crankshaft revolutions to set the piston to TDC on the compression stroke. If the pressure does not start to increase during the first revolution, continue to rotate the crankshaft. If there is pressure and the marks match, then piston No. 1 is set to the correct position.
All models
15. After the torus and as piston No. 1 is set to TDC in the compression stroke, the remaining pistons can also be set to TDC by turning the crankshaft in portions of 180° and monitoring the firing order of the cylinders (i.e. an additional turn of 180° will bring piston No. 3 to TDC, etc.).