3.23. Check of a state and replacement of spark plugs

Tools necessary at replacement of spark plugs

1 — the Candle head - Is equipped with the special elastic insert excluding a possibility of casual damage of the porcelain insulator at a candle reversing.
2 — the Dynamometer key - without being among obligatory tools, provides a reliable guarantee of correctness of effort of tightening of spark plugs.
3 — the Ratchet drive - Is used in a set with a candle head and a dynamometer key.

4 — the Extender - Depending on model and a complete set access to spark plugs can be limited by its auxiliary units in various degree therefore use of extenders of the corresponding form and design will allow to facilitate implementation of the procedure considerably.
5 — the Device for measurement and correction of interelectrode gaps of spark plugs - Is issued several types of this sort of tools - make sure that the tool is completed with the probe corresponding by the size to gaps of candles of your car.

If original candles after check of a state are established on the engine again, they have to be rolled strictly in former cylinders, - make the corresponding marking.

General information

The spark plug is the metal cover framing the ceramic (porcelain) insulator. The vertical channel in which is provided in an axial part of the isolation center the probe of the central electrode is filled. The top part of the probe is connected to the carving tip rolled in the top part of the isolation center, lower acts from below, forming a working part of an electrode. The side electrode is welded directly on metal of a cover of candle assembly and, being bent under 90 ° leaves to the central part of the lower face surface of a candle, settling down directly over an end face of a working part of the central electrode. The air gap formed between two electrodes received the name of interelectrode and is one of the main, working parameters of a candle. The size of a gap has to be exposed strictly according to the standard requirements determined by types of candles and the engine. When giving on tension VV candle (20 ÷ 50 kV) from the ignition coil in between electrodes the spark providing ignition of air-fuel mix in the engine combustion chamber is formed. Intensity of sparking actually is also defined by the size of an interelectrode gap.

One more of osnovoopredelyayushchy parameters of any candle is its kalilny number. The Kalilny number defines ability of a candle to dispersion of heat. The lower carving part of a cover of a candle (the more deeply electrodes in the combustion chamber refuel) is longer, the will be hotter its working temperature. Installation on the engine of excessively "cold" spark plugs leads to bystry education on their electrodes of oil and coal deposits, finally, that leads to emergence of admissions of ignition. Use of too "hot" candles can lead to the problems connected with ignition advancing corner uka (too early ignition), besides, there can be a diesel effect when the engine continues to work during even some time after switching off of ignition. The following rule is usually applied: at trips on a long distance with high speeds of movement it is necessary to apply colder candles, "hot" candles are suitable for operation of the car in the mode of the intense city cycle which is characterized by frequent short trips more. The best compromise is always reached when using original spark plugs, the recommended manufacturer of the car (see Specifications).

Check and adjustment


During normal operation of the car the size of an interelectrode gap of spark plugs increases on average by 0.025 mm on each 4000 km of escape that leads to gradual decrease in intensity of sparking. Carries out adjustment/replacement of candles strictly according to the Schedule of routine maintenance of the car (see the Section Schedule of Routine Maintenance of the Mitsubishi Galant/Mirage/Diamante Cars).

1. In most cases replacement of spark plugs requires existence of a special candle head (with an elastic insert inside) complete with the ratchet drive, and also a set of extenders of the drive of a key and the device for check and correction of interelectrode gaps. For a safe detachment of tips of VV of wires from shafts of spark plugs the special tool is also issued though its application and is not strictly obligatory. Use of a dynamometer key will allow to achieve the correct effort of tightening of candles.
2. It is the most correct to keep constantly in the car a set of replaceable spark plugs with the correct image the adjusted interelectrode gap. Upon purchase of new candles you watch that they met for the parameters the requirements of the engine of your car. Necessary information is provided in Specifications to the present Chapter, and also on VECI label fixed under a cowl (in case of discrepancies preference should be given to information with VECI).
3. Start a reversing of candles only after full cooling of the engine. Not to waste in vain time, use a pause for check of a condition of a replaceable set. Attentively examine new candles, - at identification of the slightest cracks in the insulator the corresponding candle has to be rejected. Measure the size of interelectrode gaps of a new set (see further).
4. The interelectrode gap of a candle is checked by introduction to it of the corresponding probe of the measuring instrument and has to conform to the requirements provided in specifications / on VECI label. The required thickness the probe has to with an easy resistance slip between side and central electrodes of a candle. Correction of a gap can be made by means of the special adaptation which is usually a part of the measuring instrument - turn in appropriately side electrode of a candle.

5. If the side electrode is located not precisely over central, correct its situation as appropriate. Make sure of lack of cracks and other damages to the porcelain insulator of a candle. Existence of any sort of defects of the insulator is inadmissible.

Removal and installation


1. In order to avoid violation of an order of ignition at connection of an electrical wiring it is necessary to make service of each of candles in an individual order.
2. Wait for full cooling of the engine. Disconnect a negative wire from the battery.

If the stereosystem established on the car is equipped with a security code before disconnecting the battery make sure that you have the correct combination for input of the audio system in action!

3. At the corresponding complete set remove the central cover. On models 3.0 l (SOHC and DOHC engines) and 3.5 l for the purpose of ensuring access to spark plugs of a back row of cylinders it is necessary to remove the top section of the inlet pipeline (see the Head Dvigatel).

4. Disconnect VV a wire from a spark plug of the first cylinder, - pull only for a tip, and not for a wire at all! It will be reasonable to use the special tool.

5. In the presence of near at hand source of compressed air, use it for removal of garbage from candle niches of the engine (the ordinary bicycle pump will be suitable for this purpose also not worse).

When using compressed air do not forget to put on goggles!

6. Turn out a spark plug by means of a face key with the special, equipped rubber insert, a candle head (in case of need previously drip in a candle niche of a little getting oil).

7. Verify the turned-out candle with the ID card given on a photographic insert that will allow to estimate the general condition of the engine qualitatively. Also estimate a condition of tips of VV of wires, replace defective components.
8. Before rolling new candles, slightly grease their carving part with the anti-taking sealant. Manually acquire one of new candles in the corresponding opening in the engine. Having made sure that the candle is not warped in a carving, tighten it with the required effort (in the presence of near at hand dynamometer key). For simplification of the procedure of a nazhivleniye of a candle pull a piece of a flexible fuel hose on its shaft. At the same time the probability of failure of a carving as at the slightest zakusyvaniye the hose will begin to be turned simply is excluded.
9. Rotary progress put a wire VV tip on a spark plug shaft.

Before connecting to candles of VV of a wire estimate their condition.

10. Repeat the procedure for the remained spark plugs, performing all operations serially in order to avoid violation of an order of ignition.
11. Establish into place all components which were removed for the purpose of ensuring access.

Coal deposits

Symptoms: Availability of soot indicates reenrichment of fuel-air mix or weak intensity of a spark. Causes admissions of ignition, complicates start and results in instability of operation of the engine.

Recommendations: Whether check the air cleaner is hammered whether fuel level in the float-operated camera is not too high, whether the air gate is jammed and whether contacts are not too worn-out. Try to use candles with longer insulator that increases the resilience to pollution.

Normal state of a candle

Symptoms: Gray-brown color and easy wear of electrodes. The Kalilny number of candles corresponds to type of the engine and its general state.

Recommendations: When replacing candles establish candles of the same type.


Symptoms: Oiling of a candle is caused by wear of maslootrazhatelny caps. Oil gets to the combustion chamber through worn-out guides of valves or piston rings. Causes admissions of ignition, complicates start and results in instability of operation of the engine.

Recommendations: Perform mechanical recovery work and replace candles.


Symptoms: Soft deposits of brownish color on one or both electrodes of a candle. A source of their education are the applied additives to oil and/or fuel. Excessive accumulation can lead to isolation of electrodes and cause admissions of ignition and unstable operation of the engine at acceleration.

Recommendations: At bystry accumulation of deposits change maslootrazhatelny caps that will prevent hit of oil in combustion chambers. Try to replace fuel brand.


Symptoms: Porous, white insulator, erosion of electrodes and lack of any deposits. Leads to reduction of service life of a candle.

Recommendations: Check whether the kalilny number of the established candles conforms to requirements of Specifications, whether the ignition advancing corner is correctly exposed, whether too poor fuel-air mix moves, whether there is no leak of vacuum of the inlet pipeline and whether valves are jammed. Check also the level of a cooler and whether the radiator is corked.


Symptoms: A rounding off of electrodes with a small congestion of deposits on the working end. Color is normal. Leads to difficulty of start of the engine in cold damp weather and to increase in fuel consumption.

Recommendations: Change candles on new, the same type.

Too early ignition

Symptoms: Electrodes are melted off. The insulator has white color, but maybe is polluted owing to admissions of ignition or hit in combustion chambers of foreign particles. Can lead to an engine exit out of operation.

Recommendations: Check kalilny number of the established candles, an ignition advancing corner, quality of mix (whether it is not too grown poor) whether the cooling system is corked and whether the lubrication system normally functions.


Symptoms: Insulators can be chopped off or burst. Also inaccurate technology of adjustment of a candle gap can lead to damage of the insulator. Can lead to damage of pistons.

Electroconductive luster

Symptoms: The insulator has yellowish color and the polished appearance. Speaks about sudden temperature increase in combustion chambers at sharp acceleration. Usual deposits at the same time are melted off, taking a form of a varnish covering. Leads to admissions of ignition at high speeds of the movement.

Recommendations: Replace candles (colder, at preservation of a manner of driving).


Symptoms: After admissions of ignition during a long period of adjournment can be loosened at preservation of working temperature in the combustion chamber. At high speeds of adjournment in flakes come off the piston and stick to the hot isolation center, causing admissions of ignition.

Recommendations: Replace candles or smooth out and establish into place old.

Short circuit of electrodes

Symptoms: Waste of products of combustion gets to interelectrode space. Firm deposits accumulate, forming a crossing point between electrodes. Leads to refusal of ignition in the cylinder.

Recommendations: Remove deposits from interelectrode space.

Mechanical damages

Symptoms: Can be caused by hit of foreign materials in the combustion chamber or arise at blow of the piston about too long candle. Lead to refusal of functioning of the cylinder and to damage of the piston.

Recommendations: Remove foreign particles from the engine and/or replace.