Detailed tips for checking the ignition system.
Try not to crank the engine with the ignition on and at least one high-voltage wire removed!
The fact is that the ignition coil, when the current in its primary circuit is interrupted, creates a voltage in the secondary circuit. It is limited by the breakdown voltage in the candle, i.e. voltage at which a spark occurs.
If you remove the high-voltage wire, then the high voltage is not limited, and there is a very high probability of electrical breakdown in another place, for example, the cover of the distributor. Therefore, it is necessary to check the spark on the candles of Japanese cars with their delicate electronics as follows. Unscrew all the candles and tie them with bare wire, for example, aluminum, in a row. Fasten the free end of the wire to the "mass", i.e. screw it to any unpainted part on the engine, and put all the tips of high-voltage wires on the candles.
Now, scrolling the engine with a starter, you can observe a spark on all the candles. If the spark is very thin (filamentous), it can be argued that the switch has failed. If the candles are dirty and wet, they must be cleaned, but it is better to replace them with new ones. Set the same gaps on the candles. The larger the gap in the candles, the better the combustible mixture in the cylinders will be ignited, but the higher the probability of failure (electrical breakdown) of any elements of the ignition system. Turn the starter 10-20 revolutions.
The spark should jump only between the central and side electrodes (in the same place), be thick, click loudly and be purple. If each electric discharge will at least by some sign differ from the previous discharge and from the discharges on neighboring candles, then it is necessary to look for the cause, because. this indicates a malfunction (in this case, the engine may start, but it will work unevenly).
Now set a gap of 2-4 mm on one candle and again turn the engine with a starter. If there is no spark on a candle with a large gap, or it changes in power with each click, then the ignition coil is most likely faulty. Another reason may be that there are leaks in the high-voltage part of the system (cracks, breakdowns, etc.).
Measure the electrical resistance of the wires. It should be about 5 kΩ and not differ by more than 1 kΩ from the resistance of other wires. Although many engines work quite tolerably even with a resistance of high-voltage wires of about 15 kOhm. Very often, the reason for the lack of spark is the failure of the switch.
The controversy surrounding spark plugs has noticeably subsided today. It seems to us that there are several reasons: the assortment of candles in stores is wider than ever, the quality of fuel in the country has improved somewhat, and the fleet has become younger and more "foreign". Nevertheless, questions continue to come to the editorial office. Some are interested in general information - why, for example, do you still need multi-electrode candles? Others are concerned about purely personal problems: look at the photo of the candle and diagnose the motor ... Answers to a dozen such questions are given below.
What are the advantages of multi-electrode candles? Is it true that there are more sparks on them than on “ordinary” ones?
Let's immediately dispel the tenacious myth about "multi-spark" candles: they do not exist in nature. There can be any number of side electrodes, but the spark discharge is always the same. Vendors often demonstrate the "multi-spark" mode on the stands, which gives the impression of a simultaneous discharge in the form of a glowing ring, but this is just an optical illusion, like in the movies.
As for the advantages of multi-electrode candles, they are. The first is the resource: due to the distribution of the load between the side electrodes, the rate of their erosion is reduced. By the way, that is why they are often installed in engines with difficult access to candles. The second is the presence of the so-called "open spark", in which the flame front does not get stuck in the interelectrode space, but goes into the combustion chamber. The combustion rate increases, which slightly increases the power of the motor and improves its efficiency. The third advantage is a relatively small number of fakes of such candles.
Flaws? Relatively high price plus the inability to set the desired interelectrode gap ...
Why do we need all sorts of "jewels" such as iridium electrodes?
A resource of 90–100 thousand km for such candles is a common thing.
Then, the service life of iridium, platinum and other “thoroughbred” candles is several times higher than that of “mongrel” ones ... At the same time, refractory electrode materials make it possible to increase the field strength in the interelectrode space, while at the same time clearing the way for the flame front. And a more powerful spark discharge, among other things, contributes to a good self-cleaning of the candle.
Why do pre-chamber candles not take root?
That which has obvious advantages takes root. In particular, a kind of "microprechambers" - recesses in the electrodes of individual branded candles - contribute to the stabilization of the discharge at the edges of such recesses. Such recesses can be both on the side (Denso) and on the central (NGK) electrodes. At the same time, there is a certain technical effect.
As for the "full-fledged" prechamber candles, they are often used in the engines of Formula 1 sports cars. The fact is that such engines operate at high speeds, at which ventilation problems simply do not arise. But at minimum idle speed, and even at low loads, the mixture in the cylinders moves much less intensively, and therefore the inner chamber of the candle actually suffocates. This is exactly what is observed, as a rule, when trying to stupidly install something pseudo-sports on your engine.
What gap should the spark plugs be?
Complex issue. The number one authority in this matter is the manufacturer of the car, more precisely, the engine. True, today such recommendations are addressed only to servicemen: the consumer is blocked by all means from access to the engine compartment (and, in general, they do it right).
Another thing is funny: even the recommended gap cannot be the same for all types of candles. For example, for the same iridium, it can certainly be more than for the classic ones! But no one usually gives such recommendations. Therefore, its specific value is always individual for the candle-motor tandem. In the general case, the larger the gap, the stronger the spark and ignition source. We also add that with an increase in the gap, the probability of shorting the electrodes by soot bridges decreases.
The danger of an excessive increase in the gap is obvious: the larger the gap, the greater the required breakdown voltage. And the discharge doesn’t care where to “shoot”: it can also pierce the coil if it decides that it’s easier for him ...
What are plasma candles?
We don't know... The question rests solely on terminology, because any spark discharge can be called cold plasma. Therefore, the attempts of individual manufacturers to call their candles plasma is a consequence of illiteracy, as well as the desire to play on the inexperience of consumers. All candles are either plasma or not: the appropriate terminology simply does not exist. But to call only candles of our own production as plasma, without honoring our colleagues in the shop with the same, is simply incorrect.
Why are candles getting thinner and thinner? Even the turnkey size used to be 21 mm, and now it is 14.
Candles with M14x1.25 threads and a large hexagon were used on engines with two valves per cylinder. At the same time, the candle most often approached the combustion chamber from the side and there was plenty of space to place it. On modern engines with four or even five valves, the only place to place a spark plug is in the center of the combustion chamber. The candle is screwed into the cylinder head through the candle well, which "steals" the space from the valves and the jacket of the cooling system. That is why it is necessary to make more and more thin candles and small diameter wells.
The spark plug pulled out of the engine is covered with a layer of oil. What is the reason?
Oily spark plugs can be a sign of relatively easy to fix problems, such as too high engine oil or clogged crankcase breathers. But it could be caused by much more formidable problems, such as worn piston rings, broken valve guides, and faulty valve seals.
It was possible to turn out the candle with great difficulty, and the new candle does not screw in completely. What to do?
It is obvious that the previous candle was not wrapped in the cylinder head. Therefore, part of the thread in the head is covered with soot and does not allow a new candle to be screwed in. In such a situation, it is best to make grooves along the threaded part of the old candle with a needle file. This will turn the candle into a kind of tap. Further, having applied a thin layer of grease to the thread of the candle, we screw it into the hole, periodically “handing it back” until we go through the entire thread. We wipe the candle hole with a swab of lint-free rags and screw in a new candle. It is advisable to use a special high-temperature lubricant or simply rub the threads with graphite.
The insulator of the candle has acquired an incomprehensible reddish color, although there is practically no soot. What is this?
Red soot on a candle is formed during the combustion of gasoline with a high content of iron-containing additives based on ferrocene. Unscrupulous manufacturers use these additives to increase the octane number of gasoline. The additive is not useful for both candles and the engine. Seeing this color of a candle, think about changing the gas station.
Should I clean the spark plugs between changes?
With a working engine, there is little carbon deposits and cleaning of the candles is not required. If the candles are covered with abundant soot during short runs, then this is an occasion to repair the engine, and not to clean the candles. In addition, the threaded holes for the candles are made of aluminum, and countless twisting and screwing can lead to thread stripping.
Fellow car enthusiasts, tell us, have you met with any unusual defects in candles?
One of the main reasons that the engine does not start when the starter is cranking is the absence of a spark discharge between the electrodes of the candles. This can be especially annoying if you need to leave urgently. We need to look for the "lost". First of all, inspect the wires and devices of the ignition system. If there is dirt, oil or water, they should be wiped with a dry cloth. Then try starting the engine again. It is possible that this will succeed. If not, inspect the high voltage wires. They should not have a "raggedy" appearance and insulation violations. Otherwise, they will have to be replaced. Check the condition of the contacts by simply rubbing the wires with your hand. The following reasons: all spark plugs do not work; faulty ignition coil or breaker-distributor; open or short to ground wires of the low voltage circuit. Let's start the search for a spark with candle wires. To do this, remove the tip of the spark plug wire from the spark plug. Bring the candle wire to the mass of the car at a distance of 5 - 8 mm and turn on the starter for a while.
"Carving" a spark of white color
Each contact opening should be accompanied by an uninterrupted white spark with a blue tint, purple, yellow and red sparks indicate a malfunction in the ignition system circuits. If there is no spark, the ignition coil must be checked separately. To do this, remove the central wire coming from the coil from the distributor cap and repeat the spark-cutting procedure. If a spark appears, then the coil is in order, and the fault must be sought in the breaker-distributor. Otherwise, either the coil is faulty or there is an open in the low voltage circuit. If suspicion has fallen on the breaker-distributor, inspect its cover from the inside. If cracks are found, the cover must be replaced. Check the center carbon contact for "hanging" by simply moving it slightly with your finger. It is useful to wash the cover with gasoline.
Apply test lamp
Breakdown of the insulation of the distributor rotor can be checked by placing the central high-voltage wire with a gap from the rotor electrode and manually opening and closing the breaker contacts. If sparking occurs in the gap, the rotor is defective and must be replaced. The low voltage circuit is easy to check with a test lamp with a voltage of 12 V and a power of not more than 3 W, which is connected with one contact to the low voltage terminal of the breaker, and with the other to ground. Set the breaker contacts to the closed position and turn on the ignition. If the lamp is on when the contacts are open, but not when the contacts are closed, then the low voltage circuit is working. If the lamp does not light when the contacts open, then the fault must be sought either in the low voltage conductors or in the primary winding of the ignition coil. If the lamp is on even when the contacts are closed, this indicates a strong oxidation of the breaker contacts, a broken wire from the breaker terminal to the lever, or a broken wire connecting the movable breaker disk to the housing. The oxidized contacts are cleaned, after which the gap is adjusted.
The quality of the spark on the spark plugs is checked in the same way as in its absence. However, it is desirable to change the gap between the high-voltage wire of the spark plug and the mass. A spark is considered good if it penetrates a gap of at least 7 mm.
A malfunction that occurs as if it does not exist at all, but it is much more difficult to find the cause of its occurrence. An ammeter will not even be able to help in this case. The best way to determine a malfunction is to turn off one or another device or section of the circuit from the ignition system and try, if possible, to get a spark without them. The appearance of a good spark indicates a malfunction of the switched off device.
When, after checking, it turned out that the spark between the spark plug and the high-voltage wire is weak, the distributor is turned off from the ignition circuit and the quality of the spark between the ground and the high-voltage wire of the ignition coil is checked. The presence of a strong spark indicates that the entire ignition system to the distributor is working, except for the distributor cap, rotor or high-voltage spark plug wires. If these parts are cracked or damaged, they must be replaced.
If, when the distributor is turned off, the spark, as before, is weak, you should carefully check all the clamps of the low voltage current circuit, cleanliness and reliability of fastening. If, even after checking the clamps, the spark is weak, it is necessary to turn off the breaker from the low voltage circuit. Its action can be replaced by an additional wire, one end of which is connected to the connection point of the capacitor wire with the low voltage wire coming from the P terminal of the ignition coil, and the other end is sharply struck by mass. In this case, the wires of the ignition coil and the capacitor must be disconnected from the terminal K of the breaker.
The occurrence of a strong spark between the ground and the high-voltage wire of the coil without the action of the breaker indicates a malfunction of the breaker.
To control the safety and reliability of the contact and isolation of the current-carrying parts of the circle from the mass, you need to check the inner circle of the breaker, the condition and gap in its contacts on all cam protrusions. When checking the inner circle of the breaker, find out whether the cam, bushings of the breaker roller, the axis and the hole for the axis of the breaker lever did not work out, the breaker panel is securely seated on the bearing.
If the spark is weak and irregular when the breaker is off, then the capacitor or ignition coil is most likely faulty. After making sure that the capacitor is working, you should check the serviceability of the ignition coil. Strong heating of the ignition coil indicates a short circuit in the primary winding. Replace the defective coil.
