Note. The description of the procedure below is based on the assumption that the BB spark plug wires are connected correctly and the ignition distributor is installed. If it becomes necessary to bring the engine to TDC in order to correct the position of the distributor, the position of the piston in the first cylinder of the engine can be qualitatively determined by monitoring the change in compression pressure through the spark plug hole. Next, you need to achieve the combination of the corresponding installation marks. 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 the camshaft, timing drive components and the ignition distributor.
Make sure the transmission is in neutral, then firmly apply the parking brake or chock the rear wheels of the vehicle. Also immobilize the ignition system by disconnecting the BB coil wire from the distributor cap and grounding it to the engine block with a jumper wire. Remove spark plugs (see chapter Settings and ongoing maintenance).
Bringing any of the pistons to the TDC position is carried out by turning the engine crankshaft in one of the ways described below. Looking at the engine from the front (from the drive belt), the normal direction of rotation of the crankshaft is clockwise:
- a) The most effective method is to rotate the shaft in the normal direction using a bolt screwed into the end of its front pin using a ratchet socket wrench - remove the lower protective screen from the passenger side of the car;
- b) Save time with remote starter switch (follow the manufacturers instructions). As soon as the piston is close enough to the TDC of the end of the compression stroke, the starter stops and further adjustment is carried out by the method described in paragraph (A);
- c) With the presence of an assistant, the preliminary cranking of the engine can be carried out in short jerks from the driver's seat under the guidance of the operator. The principle is the same as described in paragraph (b). The final adjustment, again, is done manually, using a socket wrench (see point a).
1. Remember position of the plug of connection of a candle wire of the first cylinder on a cover of the distributor.
2. If the terminal is not marked, run the wire from the spark plug to the cap and mark the appropriate label yourself (use a scriber or marker).
3. Remove the cap from the distributor and set it aside (see chapter Settings and ongoing maintenance).
4. Turn the crankshaft clockwise so that the white TDC mark on its pulley is aligned with the triangular pointer on the timing belt cover.
Note. There are two alignment marks on the pulley. The second mark is applied in red paint and serves only to set the ignition timing using a stroboscope.
5. Now check the position of the distributor slider - it should be deployed with a spout exactly on the mark on the body rim. If the slider is rotated 180°relative to the mark, therefore, the piston of the first cylinder is in the TDC position of the end of the exhaust stroke. In order to bring the piston to TDC at the end of the compression stroke, turn the crankshaft one more complete revolution (360°) counterclock-wise. Now the slider should turn around with its nose towards the mark.
6. Loosen the screw and set the inspection cover aside, thereby providing access to the alignment marks on the gear wheels of the camshafts of both rows of cylinders. Through the hole in the timing belt cover, make sure that the alignment mark on the camshaft gear is aligned with the mating mark on the rear cover.
7. When all marks (on the crankshaft pulley and camshaft gear) are aligned, the piston of the first cylinder can be considered brought to the TDC position of the end of the compression stroke.
8. Now, in order to alternately, in the ignition order, bring the remaining pistons to TDC, the crankshaft should be rotated clockwise in 120°increments, moving from cylinder to cylinder in ignition order. Put appropriate marks on the rim of the distributor housing (as it was done above for the terminal for connecting the first spark plug wire). Cranking the crankshaft will inevitably be accompanied by the rotation of the slider, the alignment of the nose of which with the corresponding mark will confirm that the next piston has been brought to TDC at the end of the compression stroke.