Removing spark plugs
Grasp the spark plug plug and pull it off the spark plug. Do not pull on high voltage wires.
Unscrew the spark plugs with a special key.
Arrange the spark plugs according to the firing order.
Tighten the spark plugs tightly without applying excessive force, otherwise the spark plug threads may damage the cylinder head.
Warm up the engine and now remove the spark plugs, being careful not to burn your hands.
When installing, do not screw cold spark plugs into a hot cylinder head tightly, because. they will then sit very tightly.
Spark plugs should be tightened to 2 Nm.
If a torque wrench is not available. then screw in the spark plug until the gasket fits, it should not be further screwed in by hand or with a key without limiting the effort.
Now turn the new spark plug 90°with a spark plug wrench (quarter turn).
A non-new spark plug, the gasket of which is already slightly flattened, should only be turned 15°further.
Checking spark plugs
Spark plugs are, to a certain extent, an indicator of the condition of the engine. The appearance of the spark plug tip will help determine if the engine is operating under optimal conditions. Beforehand, thoroughly warm up the car on a country road or highway. Control after a short trip can lead to errors. It is necessary to examine the tip of the insulator along with the central and side electrodes:
- The tip of the insulator is colored from light gray to brown: good adjustment of the carburetor or injection system, the engine runs economically.
- Severe deposits: Additives in engine oil or fuel or increased oil consumption may be the cause. You may need to change the type of oil or fuel.
- Black soot-like deposits: Spark plugs do not reach their self-cleaning temperature during frequent short trips, incorrect glow number, CO content too high.
- The tip of the insulator is painted white: the ignition timing is too far advanced, the ignition timing regulator does not work, the CO content is too low.
- Melted parts on the center and ground electrodes: glow ignition due to deposits in the combustion chamber, overheated valves, incorrect ignition timing or overheating due to insufficient cooling.
- Fracture of the end of the insulator, which is initially identified as a very thin crack: detonation combustion due to low octane fuel, incorrect ignition timing, insufficient engine cooling or lean mixture due to additional air.
- A yellowish shiny layer on the tip of the insulator: gasoline or engine oil additives have formed deposits that, when the engine is unevenly loaded, spread and become conductive - as a result of interruptions in the ignition. After using the car for a long time only for short trips, do not immediately fully load the engine.
- Oil layer on top of the electrodes and the inside of the spark plug: damage to the piston rings, valve guides or valve stem seals.
- If the electrodes and insulator of the spark plug do not show any features, but the engine is difficult to start or runs jerkily, then the cause may also be in the spark plugs. Invisible cracks in the ceramic insulator when starting a cold engine can fill with condensed fuel, preventing the ignition spark from passing. Also, under pressure, the candles may fail, although the spark slips in the removed state.
Interelectrode distances
The gasoline-air mixture or burnt gases corrode the metal electrodes of the spark plugs. The high voltage of the spark also pits small pieces of metal, causing the spark plug gap to increase over time.
For the described engines, spark plugs with different interelectrode distances are used.
If the distance is too far, an increased voltage is required to generate an ignition spark, and this can lead to misfiring. The engine may even not start at all, so spark plugs with the same ground electrode must be tucked in regularly. For spark plugs with 3 side electrodes, precise bending is hardly possible.
Selection of new spark plugs
Heat number:spark plugs must match the temperature in the combustion chamber. This number indicates how much heat the spark plug carries, i.e. can take away, itself without overheating at the same time. If the spark plug draws too much heat, it will not reach its self-cleaning temperature and the spark plug electrodes will become carbonized.
Electrodes: Candles are used both with one side electrode and with 3 electrodes «masses».
Candle thread: on all candles for the described engines, the thread length is 19 mm, the diameter is 14 mm.
Key size:the size of the hexagon for putting on the candle wrench can be 20.8 mm and 16 mm.
Seal: all spark plugs use flat gaskets that do not require additional seals.
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