2. If the marks on the high-tension wires are not visible, mark them from 1 to 4, in accordance with the cylinder numbers (The 1st cylinder is located on the engine side of the gearbox). Remove the spark plug wires by holding the wire tip, not the wire itself. Otherwise, the tip may come off the wire (see fig. 4.2).
Fig. 4.2. Removing high-voltage wires from spark plugs
3. To prevent dirt from getting into the cylinders, before removing the spark plugs, it is recommended to clean the spark plug sockets with a clean brush, vacuum cleaner or air jet (see fig. 4.3).
Fig. 4.3. Brush away dust from the recesses under the candles
4. Remove the spark plugs using a spark plug socket wrench. Keep the socket wrench aligned with the spark plug - if it is skewed, the porcelain insulator may be damaged (see fig. 4.4). After removing each spark plug, inspect it carefully.
Fig.4.4. Unscrewing the spark plug
5. Inspecting the spark plugs will help determine the condition of the engine. If the internal insulator of the spark plug is white and clean without deposits, this means that the engine was running on a lean mixture or that the spark plug is too hot (a hot spark plug transfers heat from the electrodes slowly, while a cold spark plug transfers heat quickly).
6. If the electrode and inner insulator of the spark plug are coated with a hard black layer, it means the mixture is too rich. If the spark plugs are coated with black oil deposits, it most likely means the engine is worn out or running on too rich a mixture.
7. If the inner insulator is covered with a thin layer of light brown deposits, then the working mixture has a normal composition and the engine is in good condition.
8. The spark gap between the spark plug electrodes is of great importance for the correct operation of the engine. If the gap is too large or too small, the spark power, and with it the efficiency, is significantly reduced. The required gap values are given in the section "Technical data" at the beginning of this chapter.
9. To set the gap, measure it with a flat feeler gauge, and then bend the outer electrode to the required value (see fig. 4.9). The gap is set correctly if the correct size feeler gauge passes between the electrodes with friction. Never bend the center electrode, as this may cause the internal porcelain insulator to break and the spark plug will have to be discarded.
Fig. 4.9. Determining the spark plug gap using a flat feeler gauge
10. Special devices for adjusting spark plug gaps can be purchased at most auto parts stores or from spark plug manufacturers (see fig 4.10).
Fig. 4.10. Set the spark plug gap by carefully bending the outer electrode using the adjusting device
11. Before installing the spark plugs, make sure (see Haynes advises), that the tips (at the end of the candle) tightly screwed in, and the outer surface and threads of the spark plugs are cleanly wiped.
It is often difficult to insert the spark plug correctly into the head hole without damaging the threads. To make this task easier, place a piece of flexible hose on the top end of the spark plug. The flexible hose works like a key with a universal joint and helps to easily align the spark plug thread with the thread in the head. If there is a mutual distortion, the hose will slip and will not allow the thread in the head to be damaged.
12. Remove the rubber hose (if it was used) and tighten the spark plug to the required torque (see Technical data). Install the remaining candles in the same way.
13. Connect the high-tension wires in the correct order and install all the parts removed to improve access to the spark plugs.