On the engine mod. ZMZ-4062 type A14DVR spark plugs are installed on engines mod. ZMZ-402 and ZMZ-4021 - type A14VR
Inspect the candle. If cracks are noticeable on the spark plug insulator, the threads or electrodes of the spark plug are damaged, it must be replaced.
Pay attention to the carbon deposits that cover the bottom of the candle.
If light brown carbon deposits evenly cover the spark plug with a thin layer, it does not need to be cleaned, as it does not affect the operation of the ignition system.
If there is no carbon deposits at all, this indicates that the engine is running on a lean mixture or with an increased ignition timing.
If the spark plug is covered with a matte black soot that is easily erased, this indicates that the engine is running on an over-rich mixture.
If the deposit is shiny black, this indicates that an excessive amount of oil has entered the engine cylinder.
Black carbon deposits must be cleaned using a sandblaster and then the spark plug must be blown out with compressed air.
You can clean carbon deposits from a spark plug using a stiff hair brush, after dipping the spark plug in gasoline for 20–30 minutes.
It is not recommended to clean carbon deposits with sharp metal objects: they will leave scratches on the spark plug, which will accelerate the carbon formation process.
After cleaning the carbon deposits, check the gap between the spark plug electrodes.
Check the gap only with a round feeler gauge, since when checking with a flat gauge, the depth of the recess on the side electrode, which is formed during the operation of the spark plug, will not be taken into account.
The gap should be in the range of 0.7–0.85 mm for engine mod. ZMZ-4062 and 0.8–0.95 mm for engines mod. ZMZ-402 and ZMZ-4021.
If the gap does not fall within the specified limits, adjust it by bending side electrode 1.
Bending the central electrode is prohibited - this will lead to cracks in the insulator and failure of the spark plug.
Replacing spark plugs
The engine has mod. ZMZ-4062 remove tip 1 of the spark plug with seal 2 without disconnecting 1 high-voltage wire from the tip.
Use wrench 3 to remove the old spark plug.
Then wrap a new one. Do not tighten the spark plug too much, the tightening torque of the spark plug is 31–38 Nm (3.1–3.8 kgf m).
Place tip 1 on the spark plug and install seal 2 so that the lower edge of the seal is placed on the flange of the hole in the cylinder head cover.
For engines mod. ZMZ-402 and ZMZ-4021 remove tip 1 of the spark plug without disconnecting the high-voltage wire from it.
Use a key to unscrew the old spark plug and screw in a new one. The spark plug tightening torque is 30–40 Nm (3.0–4.0 kgf m).
Place tip 1 onto the spark plug.