Note. When disconnecting high voltage wires from spark plugs, pull on the end of the wire, not the wire, as it may be damaged.
2. Remove the spark plug using a spark plug wrench. To prevent damage to the candle, install the candle key strictly along the axis of the candle.
Attention! Use compressed air to clean the spark plugs, which will prevent dirt from entering the engine cylinders after unscrewing the spark plugs.
3. Check the spark plugs for the following defects:
- 1) insulator damage;
- 2) electrode wear;
- 3) soot;
- 4) gasket damage;
- 5) condition of the insulator at the tip of the spark plug.
4. Using a wire gauge, check the electrode gap of the spark plug.
The gap is adjusted by bending the side electrode. The gap between the electrodes of a spark plug is of great importance, since too large and too small a gap changes the size of the spark, which leads to a decrease in engine efficiency. The gap must always comply with the technical requirements.
In no case should the central electrode be bent, as this can lead to breakage of the insulator and failure of the candle. Interelectrode gap of the spark plug: 1.0–1.1 mm.
5. Screw the spark plug into the cylinder head. Overtightening the spark plugs can damage the spark plug threads.
Tightening torque: 20–30 Nm.
Spark plug analysis
Visual inspection of the working part of the spark plugs can show the condition of the engine.
Dark soot:
- Re-enriched fuel mixture
- Insufficient air content in the fuel mixture
Light-colored soot:
- lean fuel mixture
- Too early ignition
- Insufficient tightening of spark plugs
Checking the functioning of the spark plugs
Connect the spark plug to the high voltage wire. Holding the spark plug with special pliers with insulated handles, connect the spark plug body to the vehicle ground.
Warning! Do not touch the vehicle body during the following operations.
The assistant should crank the engine crankshaft with a starter, while a steady strong spark should be observed between the spark plug electrodes.
If there is no ignition spark or the ignition spark is weak, check the condition and correct the following defects:
- if carbon deposits are present, clean or replace the spark plug;
- if contaminated with oil, clean or replace the spark plug;
- if the electrodes are worn or burnt out, replace the spark plug;
- if the ceramic insulator is destroyed, replace the spark plug;
- if the spark plug ring is damaged, replace the spark plug;
- in case of violation of the interelectrode gap in the spark plug, adjust the gap.