Note: The following procedure is based on the assumption that the spark plug wires and distributor are installed correctly. If it is necessary to bring the engine to TDC to adjust the distributor position, the piston position in the first cylinder of the engine can be determined qualitatively by monitoring the change in compression pressure through the spark plug hole. Then it is necessary to achieve alignment of the corresponding installation marks (see paragraph 9).
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 of the end of the piston compression stroke is used (usually the first cylinder).
The need to bring the piston to the TDC position arises when performing many procedures, in particular such as removing/installing the camshaft, timing drive components and ignition distributor.
1. Make sure the transmission is in neutral, then firmly set the parking brake or chock the rear wheels of the vehicle.
2. Immobilize the ignition system by disconnecting the electrical connectors of the distributor (see Chapter Engine electrical equipment).
3. Temporarily disable the power supply system (see Chapter Power and exhaust systems).
4. Remove the spark plugs (see Chapter Routine maintenance).
5. 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 counterclockwise. Remember that attempting to turn the shaft clockwise 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 the 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 made 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).
6. Note the position of the spark plug wire connection terminal for the first cylinder on the distributor cap. If the terminal is not marked, follow the wire from the spark plug to the cap and mark it yourself.
7. Remove the distributor cap and set it aside (see Chapter Routine maintenance).
8. Mark the housing at a point directly below the first cylinder cover terminal (see accompanying illustration).
9. Find the timing marks on the crankshaft pulley. The white highlighted mark corresponds to the TDC position. Now, turning the crankshaft in the normal direction (see paragraph 5), achieve precise alignment of this mark with the pointer on the lower timing belt cover (see accompanying illustration).
10. Now check the position of the distributor runner - it should be turned with its nose exactly on the mark on the body. If the runner is turned relative to the mark by 180°, then the piston of the first cylinder is in the TDC position of the end of the exhaust stroke.
11. In order to bring the piston to TDC at the end of the compression stroke, the crankshaft should be turned one more full revolution (360°) counterclockwise. Now the runner should turn with its nose towards the mark.
12. If all the above conditions for aligning the marks are met, the task can be considered completed – the piston of the first cylinder is brought to the TDC position at the end of the compression stroke.
13. Now, in order to bring the remaining pistons to TDC one by one in the order of ignition, the corresponding marks should be applied to the rim of the distributor housing (as was done above for the terminal connecting the first spark plug wire). Turning the crankshaft will inevitably be accompanied by rotation of the runner, the alignment of the nose of which with the corresponding mark will confirm that the corresponding piston has reached TDC at the end of the compression stroke.
(The original is located on the website: HONDABOOK)