Tools needed when changing spark plugs
1 - Candle head - Equipped with a special elastic insert, which excludes the possibility of accidental damage to the porcelain insulator when the candle is turned out; 2 - Torque wrench - Not included in the number of mandatory tools, provides a reliable guarantee of the correct tightening torque of the spark plugs; 3 - Ratchet drive - Used in conjunction with a candle head and a torque wrench; 4 - Extension cord - Depending on the model and its configuration with auxiliary units, access to spark plugs can be limited to varying degrees, so the use of extension cords of the appropriate shape and design will greatly facilitate the procedure; 5 - A device for measuring and correcting spark plug gaps - Several types of this kind of tools are available - make sure that the tool is equipped with a feeler gauge that matches the size of the spark plug gaps in your car.
If the original spark plugs are re-installed on the engine after checking the condition, they must be screwed strictly into the previous cylinders - make the appropriate marking.
1. Do not forget, during the check / replacement of candles, to also evaluate the condition of the wires connected to them.
2. In most cases, a special spark plug head is required to replace spark plugs (with elastic lining inside) complete with a ratchet drive, as well as a set of wrench drive extensions and a tool for checking and adjusting the interelectrode gaps. A special tool is also available for safely disconnecting the BB wire tips from the spark plug shanks, although its use is not strictly required. Using a torque wrench will allow you to achieve the correct tightening torque for the candles.
3. It is best to keep a set of replacement spark plugs with a correctly adjusted electrode gap in the car at all times. When buying new spark plugs, make sure that they meet the requirements of your car engine in terms of their parameters. The necessary information is given in the Specifications to this Chapter, as well as on the VECI label attached under the hood (in case of discrepancies, VECI information should prevail).
4. Proceed to turning out the candles only after the engine has completely cooled down. In order not to waste time in vain, use the pause to check the status of the replacement set of candles.
5. The gap between the electrodes of the spark plug is checked by inserting the appropriate meter probe into it and must meet the requirements given on the VECI label. The probe should slip with slight resistance between the side and center electrodes of the spark plug. The gap can be adjusted using a special tool, usually included in the meter - bend the side electrode of the spark plug accordingly. If the side electrode is not positioned exactly above the center electrode, correct its position accordingly. Check for cracks or other damage in the porcelain insulator of the spark plug. The presence of any kind of defects in the insulator is unacceptable.
6. With a cold engine, disconnect the BB wire from the spark plug of the first cylinder (see Section Checking the condition and replacing the explosive spark plug wires, cover and distributor slider). Pull only on the tip, and in no case on the wire! It would be wise to use a special tool.
7. If you have a source of compressed air at hand, use it to remove debris from the spark plug niches of the engine (For this purpose, a conventional bicycle pump is no worse).
Warning! Remember to wear protective goggles when using compressed air!
8. The spark plugs on some of the models in question are deeply recessed into the candle niches, so you will need a key drive extension to turn them out. Putting the head on the candle, connect the drive and, gently turning the gate counterclockwise, unscrew the candle (see accompanying illustration).
9. Check the removed spark plug against the condition map shown in the photographic insert to give a good idea of the overall condition of the engine. Before screwing in new spark plugs, lightly lubricate their threads with anti-seize sealant (see accompanying illustration).
10. Thread one of the new spark plugs into the appropriate hole in the engine by hand. After making sure that the candle is not skewed in the thread, tighten it with the required force (with a torque wrench handy). To facilitate the procedure for baiting a candle, pull a piece of flexible fuel hose onto its shank (see accompanying illustration). This eliminates the possibility of thread breakage, since at the slightest biting, the hose will simply begin to turn.
11. Before connecting BB wires to the spark plugs, follow the procedures in Section Checking the condition and replacing the explosive spark plug wires, cover and distributor slider.
12. The connection of the BB wire is carried out by rotational-translational movements of its tip, - the latter should sit tightly on the shank of the candle.
13. Repeat the procedure for the remaining spark plugs, performing all steps in turn to avoid disturbing the order of connecting the BB wires.
Coal deposits
Symptoms: The presence of soot indicates an over-rich air-fuel mixture or a weak spark intensity. Causes misfiring, difficult starting and engine instability.
Recommendations: Check if the air cleaner is clogged, if the fuel level in the float chamber is too high, if the air damper is stuck, and if the contacts are too worn. Try using plugs with a longer insulator, which increases fouling resistance.
The normal state of the candle
Symptoms: Gray-brown color and slight wear of the electrodes. The number of glow plugs corresponds to the type of engine and its general condition.
Recommendations: When replacing spark plugs, use spark plugs of the same type.
Oiling
Symptoms: Lubrication of the candle is caused by wear of the valve stem seals. Oil enters the combustion chamber through worn valve guides or piston rings. Causes misfiring, difficult starting and engine instability.
Recommendations: Carry out mechanical repairs and replace spark plugs.
Ash formation
Symptoms: Soft brownish deposits on one or both spark plug electrodes. The source of their formation is the additives used in oil and/or fuel. Excessive buildup can insulate the electrodes and cause misfiring and engine instability when accelerating.
Recommendations: If deposits build up quickly, replace the oil seals to prevent oil from entering the combustion chambers. Try changing the brand of fuel.
Overheat
Symptoms: Porous, white insulator, electrode erosion and absence of any deposits. This will shorten the life of the spark plug.
Recommendations: Check if the glow rating of the installed plugs meets the requirements of the Specifications, if the ignition timing is set correctly, if the air-fuel mixture is supplied too lean, if there are vacuum leaks in the intake pipeline and if the valves are stuck. Also check the coolant level and check if the radiator is clogged.
Wear
Symptoms: Rounding of electrodes with a slight accumulation of deposits at the working end. The color is normal. Causes engine start difficulty in cold, wet weather and increased fuel consumption.
Recommendations: Replace spark plugs with new ones of the same type.
Too early ignition
Symptoms: The electrodes are melted. The insulator is white, but may be dirty due to misfiring or foreign particles entering the combustion chambers. May lead to engine failure.
Recommendations: Check the glow number of the installed candles, the ignition timing, the quality of the mixture (isn't it too poor), whether the cooling system is clogged and the lubrication system is functioning properly.
Detonation
Symptoms: Insulators may be chipped or cracked. Insulator damage can also result from inaccurate spark plug gap adjustment. May damage pistons.
Electrically conductive gloss
Symptoms: The insulator has a yellowish color and a polished appearance. It speaks of a sudden increase in temperature in the combustion chambers during sharp acceleration. At the same time, ordinary deposits are melted, acquiring the appearance of a varnish coating. Causes misfiring at high speeds.
Recommendations: Change spark plugs (colder, while maintaining driving style).
Splashing
Symptoms: After misfiring for a long period of time, deposits can loosen while maintaining the operating temperature in the combustion chamber. At high speeds, deposits flake off the piston and adhere to the hot insulator, causing misfiring.
Recommendations: Replace spark plugs or clean and reinstall old ones.
Closing the electrodes
Symptoms: Waste products of combustion fall into the interelectrode space. Solid deposits accumulate, forming a jumper between the electrodes. Leads to ignition failure in the cylinder.
Recommendations: Remove deposits from the interelectrode space.
Mechanical damage
Symptoms: May be caused by foreign material entering the combustion chamber or caused by the piston hitting a spark plug that is too long. Lead to cylinder failure and piston damage.
Recommendations: Remove foreign particles from the engine and/or replace.