The design and principle of operation of the ignition system of a household chainsaw

Every saw, working on gasoline engine, is necessarily equipped with an ignition system. The main function of this assembly is to ignite the fuel inside the cylinder in time. To do this, the chainsaw’s ignition system creates an electrical discharge that pierces the space between the electrodes of the regular plugs. The functionality and efficiency of the chainsaw depends largely on the proper operation of the engine. That is why special attention needs to be paid to checking this important part of the tool.

The electronic ignition of a utility chainsaw is made up of a number of the following parts as standard:

The magneto is a separate type of alternator that operates with alternating current. When it works, it creates electrical energy, and directs it to the chainsaw’s spark plug. The device of the magneto includes a coil of inductance, on which the fixed winding is wound. The element also has a permanent magnet attached to the flywheel. When the chainsaw is running, the flywheel rotates simultaneously with the engine crankshaft.

At the right moment, a certain regular part of the device unwinds the available contacts. This causes a sudden increase in voltage and a spark between the electrodes of the factory spark plug.

This increases the risk of overheating the contacts. To exclude this, as well as oxidation of the wiring, the electrical circuit of the standard ignition system is equipped with a capacitor.

The ignition circuit of a chainsaw equipped with a non-contact base magneto is based on the action of the control coil. It acts as a voltage flow regulator. The design of the electronic unit of such an ignition system is supplemented by a capacitor, a diode and a thyristor. The latter is needed to carry current with certain voltage parameters. During the opening of the thyristor, the capacitor starts to discharge, thus creating current inside the turns of the basic primary winding.

The current is then converted to a high-voltage DC voltage, which creates a breakdown in the standard spark plug located in the cylinder. The standard chainsaw electrical network operates on the pulse principle simultaneously with the progressive cyclic motions of the engine cylinder and the rotation of the crankshaft.

How to determine the advance angle of the internal ignition?

The construction features of the integrated ignition coil ensure that the optimum factory position of the moving piston and the spark plug discharge are matched. When a 4-stroke engine is running, the spark must strike before the piston reaches the top end position. This is because these engines need more time to burn the fuel. In their factory set, the speed of the internal combustion engine parts is equal to the speed of the planned ignition of the fuel filled. So the piston has time to travel a certain distance from the moment the spark is created to the place where the spark plug is located. To the period in which the burning gases are guaranteed to have time to create extremely high pressure readings.

During the mass assembly of engines in standard factory conditions, the manufacturers do not perform the ignition adjustment. Instead, marks are left on the rotating elements, which must necessarily be aligned during installation.

How to check the magneto of a chainsaw

Magneto, butterfly, module is the ignition coil. It may have absolutely nothing to do with the failure of the tool, and the cause is only hidden in the gap or other. But in some cases, it’s what causes the malfunction.

To check the cylinder itself, you should also, as in the above case, use the elimination of components from the chain. Or in other words:

  • Visually assess the condition of the cylinder housing for cracks and other visible defects;
  • Check the cleanliness of the current connections of the various assemblies and elements;
  • diagnose the insulation and the serviceability of the armature, the reliability of the fixing, the absence of rust, etc.п;
  • assess visually the condition of the spark plug cap;
  • Checking the serviceability of the spark plug;
  • diagnose the circuit breaker, which is especially relevant for chainsaws made in China.
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Again, as in the case described above, certain items are excluded from this chain, thereby the cause of the malfunction is found.

  • Measuring the resistance of the magnetos. However, this option is not always applicable, because you first need to know the resistance parameters. In addition, in order to form the required BB pulse, it is necessary to separate the indicators of the various semiconductor elements. As a rule, as a sign of malfunction is the ringing of the circuit through the BB wire and the minus. Should show either “broken circuit” or high resistance.
  • You can check it this way. use a device that checks the presence of the spark. It is installed in the gap in the circuit between the cylinder’s HV wire and the spark plugs. The disadvantage of this method is that such a device is very expensive, it is mostly used in serious repair services.
  • An “old-fashioned” way of checking, which allows you to save money on an expensive device. It is used at one’s own risk when no other solution is available. The way to check it is to unscrew the cap from the plug and put a nail in it. The spark plug is reinserted. Nailail should be 6-7 mm from the cylinder. The chain saw starts. The spark is examined: it should be bright blue in color, if not, it is a sign of a malfunctioning cylinder.

The “old-fashioned” way to check the cylinder has many disadvantages. First of all, this applies to the electrical nodes in the system, which can easily go bad. The distance between the cylinder and the nail may vary depending on the different models of tool.

As for the magneto adjustment, it boils down to the examination of the groove on the flywheel. ignition timing does not need to be adjusted for the majority of today’s saw models. But it is possible to determine its exposure only by the angle between the mark after the groove on the flywheel and the magnets installed, again, on the flywheel.

Correctly and precisely set the clearance between the magneto and flywheel. that’s what’s important.

It should be known that the cylinder on chainsaw systems is installed in the fan fuselage near the flywheel. The coil in contact with the flywheel’s magnetic field generates the energy for the spark.

Chainsaw Ignition Coil Test Step by Step Easy Test Covers All Chainsaws

To replace the coil itself will be much more difficult, because the place of installation is too awkward. The installation of a new coil should be done so that the base of the coil is 1-1,5 mm above the flywheel magnets.

In some cases it is recommended to check also the crankshaft bearing for play.

Ignition coil (magneto) of Chinese chainsaw 38cc

Ignition coil or magneto of a Chinese chainsaw with an engine capacity of 38 cc.see.

check, ignition, coil, chainsaw

Before installing the ignition coil (magneto) with the article “How to check the ignition coil (magneto) of a chainsaw (lawnmower, etc.д.)”

To prevent premature damage to the ignition coil, we strongly recommend that you do not attempt to start the tool (pull the starter) with the switch in the “OFF” position.

Following is a partial list of matching saws.

check, ignition, coil, chainsaw

Chinese chain saws with an engine capacity of 38cc: Forza 3816, Sturm!) GC9937, Energomash PT-9937, BauMaster GC-99376X, Huter BS-40, Champion (Champion) 137, SD-Master 3816, Patriot (Patriot) PT3818, etc.

This ignition would not work on older 38cc saws such as Champion 138, Sturm GC-9938 and their analogs.

Check condition and replace with new ones if necessary

Ignition coils

A modern chainsaw is a reliable enough machine, and with proper care, it usually does not cause any problems to its owner. However, breakdowns do occur, and the greatest amount of time and effort takes diagnosis of engine problems. The following symptoms are indicative of its malfunction

  • the engine works unsteadily, with interruptions;
  • The unit starts, but soon stalls;
  • the engine does not develop the necessary power, works well at idle speed, but stops when the load increases;
  • the engine does not start at all.
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Any of these malfunctions can indicate a breakdown in the ignition system. It consists of several components, each of which should be subjected to diagnostics. The chainsaw ignition coil fails rarely, so you should first check the spark plug. it’s cheap and easy to replace. Pay attention to the integrity of the ceramic insulator, signs of electrode wear, the condition of the spark plug cap. Then check the condition of the wires going from the coil. constant vibration can be the cause of their internal breakage if the insulation is undamaged. And if you do not find anything criminal, then you probably need a new ignition coil for a chainsaw, as this part cannot be repaired. Its price is quite affordable, and you can order spare parts in our online store “Expendable” with delivery to all regions of Ukraine, including Kiev, Kharkov, Odessa, Dnepropetrovsk and other cities.

Problems with chain saw ignition modules

Ignition modules and coils sometimes suffer breakdowns. When everything else is checked, the suspicion is. When they fail, one of two things usually happens. The obvious symptom is no spark. The only thing you can do is to replace the module with a new one. Or better yet. Try swapping it out with the saw you are using. If the spark after replacing the modules did not appear, apparently, you missed something.

Replacing the module is the only reliable way to check the spark. All kinds of testers, as practice shows, are not true. The only reliable test. coil replacement. Another symptom that indicates a bad electronic module or coil is a spark that becomes weak when the saw becomes hot. If the saw won’t start after refueling, it’s likely the engine heat has eliminated the spark. A weak ignition coil can sometimes provide enough spark to start and run the saw until it is properly warmed up. When the saw and coil become respectively hot, the transistor resistance increases and the spark becomes weak. Symptoms: the saw starts and works fine in the store, for example, but at work the saw dies and will not start until it cools down. It can be difficult for the store to prove this malfunction.

This is a load simulator used to diagnose saw engine with ignition systems that have heat related problems. It is an adjustable pneumatic brake system, the motor thinks that the wood cutting is performed. With this tool, we can heat the saw engine to operating temperature in a very short time. Because the load is constant and adjustable, we can easily monitor the motor for misfires or other operational defects that would be difficult to observe when sawing wood.

It also makes sense under these conditions, after overheating does not start, to try to unscrew and screw the tank cap. Having vented the accumulated fuel gases. If the saw starts after that, you can guess for yourself.

Inspection Recommendations

Many novice car enthusiasts are interested to know how to remove the ignition coil, because it is necessary to carry out the procedure with the disassembled device. It is also worth knowing about the main types of problems that arise during the operation of this module.

The main faults

In older cars, it is quite easy to find the device, because it was installed in the field of visibility of the motorist. If you start the search with the center conductor of the ignition distributor, there is no problem. You can also quickly find and individual coils, most often located above the spark plugs.

However, in some models it may be difficult to remove them, because you must first dismantle parts of the propulsion system. Thus, first of all, you need to determine the location of the right element, and then understand how to check the ignition coil with a tester.

Among the main signs of malfunction of this module should be noted:

  • No spark and the engine can not start.
  • The power plant trots during operation and it is especially noticeable in high humidity.
  • During computer diagnostics, ignition skips in some cylinders were detected.
  • Decreases in traction are observed when the accelerator pedal is depressed.
  • The powertrain has difficulty starting “at idle” and especially when the air temperature is low.
  • Serious overheating of the device is observed.
  • The conductors that fit the device have changed color.
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Often vehicle owners are partly to blame for problems with this element themselves. Wishing to save money, many decide to use non-standard parts. If we talk about the most common faults, we can note:

  • Re-polarizing the battery.
  • Frequent overheating of the coil.
  • Shorted electrical wiring.
  • Mechanical damage to the device.
  • Sudden temperature fluctuations.

Running diagnostics

It is also necessary to read the information about how to ring the ignition coil with a multimeter, because this information will be useful to all owners of mechanisms equipped with gasoline power units. This measuring device allows you to monitor the voltage and resistance. Set the switch of measuring instrument to “200 Ohm” and by placing the feeler gauge to the terminals “” and “K” measure the resistance value of the first coil winding.

It should be in the range of 0.2-3 ohms. In the next step, the multimeter switch should be set to “20 kOhm” mode and the resistance between the central contact of the high-voltage conductor and the “K” terminal should be checked. The device in this situation should show a resistance of 2-4 kohms.

The most common difficulty arises in the diagnosis of double coils, as the primary winding is connected to the connector. A multimeter can only be used to test it if the user is familiar with the coil diagram. Diagnosis of the secondary winding is carried out between the two high-voltage conductors.

Without a certain set of knowledge in the field of radio electronics it will be quite difficult to determine the fault of individual coils, as it is necessary to assemble the circuit diagram. However, there is one way that always works. If the power unit is tripping, you should start disconnecting the coil terminals in series while the engine is running.

If after that the engine started doubling, then there is no spark in that cylinder. A computer diagnostic can also be performed to solve this problem. But even if during the inspection there is a cylinder number without a spark, it is not possible to unequivocally say that the coil is defective. Knowing how to check the resistance of the ignition coil with a multimeter, you can quickly determine the source of the problem and replace the failed element. Many car enthusiasts replace on foreign cars branded coils with devices from VAZ, as they cost significantly cheaper.

The starter motor device

Often, chainsaw manufacturers equip their units with starters that work on almost the same principle, namely: in the groove of the saw housing is a handle, through which the cord is passed. When the handle is suddenly raised, the cord is also pulled, which engages the drum of the ratchet mechanism. This is how the spike drum, which is located on the shaft, is actuated. At this time, the crankshaft makes several revolutions, leading to compression of the fuel mixture, which at this point is between the cylinder head and the piston. When the handle is lowered, on the contrary, the ratchet and the studs lose their contact, which leads to the stopping of the shaft.

Design and principle of chain saw starter

Increasing the power of the chainsaw increases the amount of fuel mixture that must be ignited when starting the chainsaw. In such a case, to start the engine it is necessary to increase the number of pulls of the starter cord. To accelerate the return of the drum mechanism, manufacturers use a special steel starter return spring, which has excellent elasticity.

If the spring is broken you must: remove the cage mechanism, pull out the spring, fixing the upper part of it with your finger and pulling the starter handle a little to the side. Then, wind the new part, avoiding kinking and twisting the new spring element, then carefully fix the cage.

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