Checking and replacing spark plugs
1. Proper functioning of spark plugs is vital to the performance of the engine. Installed candles must match the type of engine (see technical data).
2. The type of spark plugs recommended for use in your car's engine are listed in the Owner's Manual that came with your car when you bought it.
3. If the correct type of spark plug is used and the engine is in good condition, the spark plugs will not need to be serviced between scheduled replacements. Cleaning candles is rarely necessary. It should be carried out with a special tool so as not to damage the ends of the electrodes.
4. A special socket wrench with extension is required to remove and install spark plugs. This wrench has a rubber grommet inside that separates the porcelain insulator from the inside of the wrench and protects the spark plug from damage and keeps the spark plug from falling out during insertion and removal. To check and adjust the gaps in the candles, you will also need a set of probes, as well as (Ideally) torque wrench for tightening the spark plug to the required torque.
5. Open the hood. Access to candles from above is not difficult. Pay attention to the laying of the high-voltage spark plug wires and their fixation with clamps along the groove located in the block head cover. In order not to mix up the wires, work with candles one by one.
6. If there are no markings on the high-voltage spark plug wires, mark them with numbers from 1 to 4 in accordance with the cylinder number (cylinder numbering starts from the camshaft drive belt). Pull the wires from the candles behind the rubber caps, sealing the holes in the block head (see fig. 29.6) Pull on the rubber cap. and not by the wire, so as not to tear it from the candle.
7. Before removing the candles, it is recommended to remove water and dirt from their sockets with a rag, clean brush, compressed air or a vacuum cleaner.
Attention! Wear protective goggles when working with compressed air!
8. Turn out the candles with a special key (see fig. 29.8. a, b). Keep the head aligned with the candle - if tilted, the porcelain insulator may be damaged. Remove the candle from the socket.
9. If the spark plug is difficult to turn, inspect the head threads and conical sealing surface for wear, corrosion, and damage. If you find these symptoms, consult your dealers for a repair method.
10. After removing the candles, check them in accordance with the recommendations below. Inspection of the spark plugs provides information about the condition of the engine.
- A) If the toe of the spark plug insulator is clean and white, this indicates that the engine is running on a lean mixture.
- b) If the tip of the electrode and the toe of the insulator are covered with black scurf, this indicates an overly enriched mixture.
- V) A black and oily spark plug indicates too rich a mixture or excessive engine wear.
- G) If the toe of the insulator has a tan or grayish brown coating, this indicates a normal mixture and, most likely, good engine condition.
12. The size of the spark gap is of great importance. When it deviates from the nominal value, the spark efficiency decreases. Adjustment must be carried out in accordance with "Technical data'. Keep in mind that new spark plugs don't necessarily have the correct gap, so they need to be checked as well.
13. Special spark gap adjustment tools are available from auto supply stores (see fig. 29.13).
14. To adjust the size of the spark gap, measure it with a probe, and then bend the outer electrode until the regulated value is reached. The inner electrode must not be bent due to possible damage to the insulator and failure of the candle. The spark gap is normal when a probe of a regulated size fits snugly into it. If the outer electrode is offset from the axis of the inner electrode, then it must be carefully bent until aligned with this axis (see fig. 29.14).
15. Before installing the candles, check the cleanliness of their external and threaded surfaces, as well as the tightness of the threaded tips on the outer end of each candle. Brown spots on the insulator just above the metal body of the spark plug are perfectly acceptable. They are not evidence of a leak between the housing and the insulator.
16. Before installing the spark plug, make sure that the threads and sealing surface in the block head are perfectly clean. Wrap the brush in a clean cloth and wipe the sealing surface. Apply copper-based lubricant or anti-seize to the threads of each spark plug. Screw in the spark plugs by hand if possible. Screw the candles without distortion so as not to damage the threads in the block head - remember that the block head is made of aluminum alloy and it is very easy to damage the threads in it.
17. Tighten the spark plugs to the correct torque. If you don't have a torque wrench, tighten the spark plugs 1/16th of a turn, no more. Do not tighten the candles with excessive force, otherwise the candles or the head of the block may be damaged when unscrewing.
18. Attach the high voltage wires in place by wiggling the sealing caps so that they sit on the ends of the candles and enter the head of the block.
Checking high voltage spark plug wires
19. When replacing spark plugs, always check the high voltage wires. Inspect the wires first when the engine is running. In a dark room (but always with good ventilation) watch the wires. Do not touch moving parts. In the event of a wire failure, sparking will be noticeable on it.
20. Check the wires one at a time so as not to disturb the order of flashes in the cylinders. Proprietary wires are marked according to cylinder numbers. If there is no such marking or it is worn out and poorly visible, apply it to the wires yourself. To do this, take a piece of adhesive plaster, write a number on it and wrap the wire around it. The numbers on the wires must match the numbers of the cylinders (cylinder numbering starts from the camshaft drive belt). Pull the wires off the spark plugs.
21. Inspect the inside of the rubber boot and wire lug for corrosion, which is usually a white, loose scum. If there is corrosion, clean it with a brush. If the corrosion cannot be removed or if the tip has poor contact with the spark plug, replace the wire with the tip. Then put the tip on the candle and check the reliability of their contact. In case of loose contact, remove the tip again and carefully bend the metal petals inside the case until the contact becomes tight.
22. Wipe the entire wire with a clean rag to remove grease and dirt from it. While the wire is clean, inspect it for burns, cracks, or other damage. Do not excessively bend or pull the wire - this may lead to breakage of the inner conductor.
23. Disconnect the wire from the ignition coil, to do this, squeeze the clamps of its tip and pull it off the coil terminal. Check the connection for corrosion and tight contact in the same way as for the spark plug tip.
24 If you have an ohmmeter, measure the resistance of the wire by connecting the meter to its ends (see fig. 29.24). If any wire resistance exceeds 30,000 ohms per meter, replace the entire wire set.
25. Connect the wire to the ignition coil in accordance with the number marked on the terminal.
26. Check up in the same way other high-voltage wires. At the end of the test, connect the wire to the coil and to the candle, paying special attention to the reliability of the connections. If significant corrosion of contacts, burns, cracks and other defects of at least one wire are found, replace the entire high-voltage wire harness together with lugs and covers. When replacing the wiring harness, disconnect the old wires and connect the new ones one at a time.
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