If the ignition is too early, the working mixture burns out prematurely and the gas pressure in the cylinder increases excessively even before the piston arrives at the V.M.T. idling at low crankshaft speed.
To check the ignition timing on the car, there is a scale 1 (see fig. thirty) in the hatch of the clutch housing and mark 2 on the flywheel. One division of the scale corresponds to 1°of rotation of the crankshaft. When the mark on the flywheel is aligned with the middle (long) by dividing the scale, the pistons of the 1st and 4th cylinders are in V.M.T.
When running the engine on a stand at service stations, you can set the ignition timing using the marks on the crankshaft pulley and on the front cover of the camshaft drive (pic. 114).
You can check and set the ignition timing using a stroboscope in the following order:
- connect clamp «plus» stroboscope with terminal «plus» battery, and the clamp «masses» with terminal «minus». Connect the stroboscope sensor clamp to the high voltage wire of the first cylinder;
- start the engine and direct the flashing stream of strobe light into the hatch of the clutch housing; if the ignition timing is set correctly, then when the engine is idling, the mark on the flywheel should not reach the middle division of the scale 1 by one division (see fig. thirty);
- to adjust the ignition timing, stop the engine, loosen the ignition distribution sensor fastening nuts and turn it to the required angle. To increase the ignition timing, the distributor sensor housing should be turned clockwise, and to decrease it, counterclockwise.
For the convenience of adjusting the ignition timing, there are divisions and signs on the flange of the ignition distributor «+» and «—», and on the body of auxiliary units - the mounting ledge (pic. 115). One division on the flange corresponds to eight degrees of rotation of the crankshaft.