How to Test a Chainsaw Coil with a Multimeter
You have brought a chain saw for repair and the handwheel is rubbing the ignition coil. The person could fix it himself, but didn’t know how to set the gap.Good afternoon dear subscribers and guests of the channel.
There are only two reasons why the flywheel starts to scratch the contact of the ignition coil. The first is incorrectly adjusted clearance or loosening of the coil mounting screws. The second is the wear of the crankshaft bearings, as a result of which there is excessive play and the flywheel will catch on the coil. In this case, the play adjustment will not help. You need to disassemble the engine and change the bearings.
You can notice the malfunction by characteristic strips on the flywheel (in the area of magnets) which remain from the contact with the ignition coil. You can see them clearly in the photo below.
The first is to check the play on the crankshaft bearings after finding the characteristic stripes. To do this, we remove the starter, turn the flywheel so that the magnets look away from the ignition coil in the opposite direction, and try to wiggle the flywheel with the crankshaft.
If you have play, even a small one, you need to remove and disassemble the engine. If there is no play, you just adjust the engine and the problem will disappear.
The clearance between coil and flywheel should be between 0.25 and 0.35 mm. If there is no play, you only need to remove and disassemble the engine. is not desirable.к. It will affect the quality of the spark, which in turn will affect the performance of the engine. As you can see in the photo in my case there is no gap at all.
to set such a gap by eye is almost impossible, you need to use a special device, at least so recommend the chain saws manufacturers. But we are thrifty people and are not used to paying for something we can do without. Let them pay over there, and we’ll use our wit and ingenuity and do with improvised means, thanks God we have enough of them.
For the adjustment we need to make a spacer from a material that is not magnetic and has a thickness of 0.25 mm. A piece of plastic from a lemonade bottle is ideal for this. I usually cut it out of a can. This is roughly what it looks like.
Major malfunctions and troubleshooting
If the saw fails to start the first time, there may be several reasons. Most often the problem is with the spark plug:
- Worn electrode or damaged ceramic insulator;
- Loose fit of the removable cap (if present);
- Wandering of the spark along the ceramic winding, a sign of which is a brown residue on the outer sheath;
- Cracks in the spark plug cap (a saw with this problem will continue to work, but may hurt the user when touched).
If there is no problem with the spark plug, it is advisable to inspect the wires coming from the coil. They can be broken or have other mechanical damage. Wires can break inside the insulation, so sometimes visual inspection may not detect it.
The cause of the failure may lie in the toggle switches. It is easy to check them. To do this, you must disconnect the wires from the module, and then check the ignition. If the spark appears after shutting off, the switch needs to be replaced.
The main problems and troubleshooting
If the saw cannot be started the first time, there may be several reasons. Most often the problem is related to the spark plug:
- Electrode wear or damage to the ceramic insulator;
- Loose fit of the removable cover (if present);
- spark wandering along the ceramic winding, a sign of which is a brown residue on the outer sheath;
- cracked spark plug cap (a saw with this problem will continue to work, but may hurt the user when touched).
If no problems were found with the spark plug, it is recommended to inspect the wires coming from the coil. They may be broken or have other mechanical damage. It is possible that the wires inside the insulation are torn, so sometimes it is impossible to detect these irregularities by visual inspection.
The cause of the malfunction may lie in the toggle switches. It’s easy to check them. To do this, disconnect the wires from the module and then check the ignition. If the spark appears after disconnection, then the switch must be replaced.
Check the ignition coil on the chainsaw
If the preliminary steps did not help in identifying the cause of the chainsaw malfunction, it is necessary to check the saw’s ignition coil. The diagnosis is carried out in several steps:
- Measure the resistance of the coil using a multimeter. For this purpose, it is necessary to know the optimum parameters, which are specified in the operating instructions. However, because of the use of semiconductor elements in the system, when you try to “wire” the coil, the result will be a “Circuit Breaker” reading. That’s normal. A positive test result is a sign of malfunction. Т. е. if it was possible to determine the resistance of the coil with a special tool, it is definitely faulty.
- Check for sparks with a special tool. This device should be installed in the gap between the spark plug and the ignition coil’s high-voltage lead of the saw. The readings will be shown on the display. This method of testing is more often used in service centers, since the device required for this is expensive, and the costs will not be commensurate with the benefits rendered.
- Test the coil with the spark plug, t. е.perform a homemade ignition. To do this, it is necessary to unscrew it and then put the body against the cylinder. Now you need to pull the starter and observe the spark. But this method gives only an approximate result, because the flywheel turns faster because of the unnatural position of the spark plug.
If none of these methods are successful, or if you need to perform a field inspection, you can do the following:
- Remove the cap from the plug, insert a nail without a cap in the core at a distance of 6-7 mm from the cylinder. This should be done as carefully as possible in order not to damage the part.
- Perform the steps required when winding the tool. Now you need to look at the spark plug and its color. If there is no malfunction, the spark will be strong and the color will be bright blue.
This method can be used as a last resort and only if there are no electronic assemblies, and it is important to follow the rules:
- the spark plug must not be completely unscrewed, as this may cause the flywheel to rotate more quickly, which is not the correct way to run the engine;
- it is necessary to place it at a distance that corresponds to the compression model and the dielectric properties of the fuel mixture, so this parameter can be seen in the manual (the value of 6-7 mm is an average).
Problems with chain saw ignition modules
Ignition modules and coils sometimes fail. When everything else has been checked, they are suspected. When they fail, one of two things usually happens. The obvious symptom is no spark. The only thing you can do is replace the module with a new one. or better yet, try to swap it out of the saw you’re using. If the spark did not appear after replacing the modules, you must have missed something.
Replacing the module is the only reliable way to check the spark. All kinds of testers have been shown to be untrue. The only reliable test is to replace the coil. Another symptom that indicates a bad electronic module or coil is a spark that becomes weak when the saw gets hot. If the saw does not start after refueling, it is likely that 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 the coil get hot, the resistance of the transistor increases and the spark becomes weak. Symptoms: the saw starts and runs fine in the store, for example, but at work the saw dies and will not start until it cools down. It can be hard for the store to prove this malfunction.
This is a load simulator used to diagnose saw motor with ignition systems that have heat related problems. It’s an adjustable pneumatic brake system, the motor thinks it’s cutting wood. With this tool, we can get the saw’s motor up to working temperature in a very short time. Because the load is constant and adjustable, you 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 unscrewing and screwing the tank cap. releasing the accumulated fuel gases. If the saw starts after that you can guess.
About chainsaws and how they don’t work
A chainsaw is not such a difficult installation in itself. But having the least initial knowledge is essential to find and fix any defect.
Modern electronics have progressed so much that they have revolutionized the tool world as well. Today’s saws are lightweight and powerful at the same time and have electronic ignition systems.
Chainsaw ignition system
Not so long ago, saw ignition systems were cam-type. That had a lot of drawbacks: Heavy, complicated, expensive, and more. And the biggest disadvantage of the archaic ignition system is the difficulty of winding. Some model saw systems couldn’t produce a spark at all, enough to flash at crankshaft speed.
Modern systems are almost trouble-free. The saw models are lightweight and rugged, the coil is made more professional and lasts almost without failure. Problems do occur, however, but in most cases these can be corrected by your own efforts.
Consider the main types of chainsaw malfunctions associated with the flywheel and ignition system.
As a rule, the most common ailment of modern chainsaws, involves the absence of a supply spark. The same directly depends on the shift of the gap (gap) between the cylinder and the flywheel.
Chainsaw spark problem
Common installation failures are always associated with the ICE. Problems arise in the ignition system, the fuel intake module, the internal components of the engine itself.
As for other chainsaw parts, malfunctions there are usually due to brake mechanism failures, poorly functioning lubrication, etc.д.
If the difficulties of starting are related to the engine, then most often these symptoms are observed:
As always, experts recommend identifying fault factors by the method of exclusion. In other words, you need to go through the chain, diagnosing each node, each link.
Chainsaw ignition module failure is the most common reason why the tool’s engine won’t start. It is recommended in most cases to start troubleshooting from here.
Chainsaw ignition module
- First of all, carefully check the spark plug by carefully removing the armored wire from the head and unscrewing the plug from its seat with a special wrench;
- second is to check the spark plug by jerking the starter with the spark plug wire cap on;
- Checking the gap is the main topic of our article (more below).
So, a faulty spark plug will be clearly evidenced by its wetness. Wet spark device for ignition of the fuel-air mixture indicates that there is an overabundance of fuel in the system, the carburetor is not properly configured or there are problems in the NW.
Check the spark plug only after it has been dried. Т.е., it should be cleaned well with a napkin, the internal combustion engine should be dried, the feeder should be plugged, and then the starter should be started a couple of times to get the excessive fuel mixture out.
Then put the spark unit back in place and recheck everything.
Black carbon on spark plug
In general, the spark plug can tell you a lot about the entire ignition system. If the spark plug has a black carbon residue on it, it is an indicator of a malfunction in the petrol mixture supply lines. Here either the petrol to oil ratio is wrong or the carburettor needs to be readjusted. In some cases it also happens with low-quality oil.
Clean black carbon deposits off the spark plug with a needle or other sharp object. Then the electrode is cleaned with emery paper until a metallic sheen is felt. The spark plug is put back in place, and everything is checked again.
Next step: check the spark feed. The spark plug skirt is led to the cylinder and the starter starts. If you have a bluish spark at a distance of 2-3 mm, you are fine. A spark gap of 0.5 to 1 mm is already considered as a fault. There may be no spark at all, and this is also a big problem. Maybe it’s a broken wire.
And here we come to the subject of our article. The chainsaw may not start because the gap between the ignition and the flywheel magneto is broken. This play should be within 0.2 mm. Checking is very simple: a special gasket is placed between the flywheel and the cylinder. If it goes in normally, not too loose and tight, then the gap is normal.
The saw’s flywheel itself is round, and checking it with an ordinary feeler gauge is not possible. The gap would be more qualified to put a special template, but it is not always possible to get it. And not everyone can afford to buy an expensive gauge for a single use.
Gap between the magneto and flywheel
However, instead of a foreign gauge you can use a cut off strip from a 1-2 liter plastic container from a juice bottle.
Advice. It is recommended to cut the plastic strip where there are no embossed irregularities.
chain saw ignition. Device, breakdowns and troubleshooting, reviews
A chainsaw, like any device that runs on an internal combustion engine, has an ignition system. It ignites the fuel-air mixture in the engine cylinder. This occurs through the delivery of an electrical discharge, which pierces the space between the electrodes of the spark plug.
It is clear that without ignition of fuel, no engine will start and will not work. But that’s not the only problem: the chainsaw’s performance depends on how accurately the ignition is set. In other words. in time or not in time the fuel is ignited. That’s why a chainsaw with a knocked down setting needs to be repaired. You can have an experienced mechanic fix it, but you can also do it yourself.
Important: New chain saws come with the ignition adjusted, there is no need to disassemble and reassemble the tool, immediately after purchase.
Some Chinese chainsaws come with poor-quality spark plugs. it may make sense to have several spark plugs in the kit.In our review, we will introduce you to the device and the principle of the ignition system, its main problems and ways to fix them.
All two-stroke gasoline engines have a similar operating principle and therefore their ignition system has a similar structure and design.
Chainsaw ignition device:
- Magneto: a device that converts mechanical energy into electrical energy, providing a current pulse to the chainsaw‘s spark plug;
- Spark plug: designed to ignite the fuel-air mixture, through the discharge that occurs between the electrodes;
Spark plugs can be spark plugs, arc plugs, glow plugs, and catalytic plugs. Chainsaw devices use spark plugs for 2-stroke engines. A schematic diagram of the ignition of a chainsaw is shown in the picture.
Most often we think about the repair after the chainsaw does not start or there are visual signs of serious malfunctions.
Signs of ignition failure:
- The chain saw starts, but it runs rough (Trojit), often sneezes and shoots;
- Power of the chain saw has noticeably decreased;
- When you press the gas pedal suddenly, you see sagging of the engine;
- The chainsaw does not start well when cold, it throws up heavily until it warms up;
- Significant increase of fuel consumption;
If your chainsaw is malfunctioning, it’s time to diagnose, adjust, or possibly repair the ignition system.
First of all, it is necessary to inspect the spark plug, if or on it accumulated a lot of soot, the cause of the malfunction is most likely related to the work of the carburetor, piston group or fuel quality. If visually the spark plug looks serviceable, it is not plugged and it is dry. make sure there is a spark.
- Unscrew the spark plug and put the ignition cable on it;
- Using insulated pliers, press the spark plug threads against the motor housing;
- Pull the starter grip sharply and check for a spark;
Spark plug with chain saw nut
If there is no spark, replace the spark plug with a new one and test again. After checking that the spark is present, start the engine. But what if there’s no spark, even on a good spark plug?? Continue troubleshooting:
- Test the electrical cable for breaks and insufficient contact with the spark plug. Check the serviceability of the spring in the cap of the spark plug and the presence of contact with the armature cable;
The best way to check for a flawless spark plug is to use a tester.
You can set the correct gap with a feeler gauge, they are not in short supply and are available for a small fee.
Troubleshooting with a multimeter
To determine the fault of the ignition coil you can also use the so-called hardware method. However, for this you must have a multimeter, which is used for diagnostics.
Step by step diagnosis of the ignition with a multimeter:
- Turn the multimeter to the position where the needle is at the 200 ohm mark.
- Read the instruction manual of the chainsaw. determine the optimal resistance for the coil winding installed on our model (in the majority of modern chainsaws this parameter varies from 3 to 5 ohms).);
- Connect a multimeter to the primary winding of the coil and measure the resistance, if it is normal continue testing;
- Connect the multimeter to the secondary winding of the coil, compare the readings with those specified in the operating manual;
- We connect the multimeter to the hole in the coil, where the wire is inserted. if the reading is satisfactory, we can conclude that the coil is serviceable. If the measurement results are far from optimal, you will have to replace the unit (coil) with a new one;
Adjusting the ignition
As we have already noted, you can adjust the ignition system in the workshop, as well as at home. For this you need an ordinary wrench, a screwdriver and a 0.4 mm feeler gauge (you can make the feeler gauge with your own materials. ordinary paper for a photocopier, a plastic bottle, etc.).п.).
Step-by-step adjustment of chainsaw ignition:
- Diagnose the problem;
- Remove the protective cover;
- Remove the module with the candle holder and cable. Carry out a visual inspection of them, if necessary replace them with a new one;
- Install the ignition module, but do not tighten the fixing screws as far as they go;
- Ignition module and flywheelDetermine the area on the flywheel with a magnet;
- Align the gap properly, according to the parameters specified in the operation manual;
- Tighten the screws fixing the module to the stop, check the settings with a dipstick, if necessary re-adjust;
- Put the protective cap back on and check the spark plug;
- Screw in the spark plug, start the chainsaw;
Important: during the repair of chainsaw ignition, special attention should be paid to the alignment of the correct gap between the module and the flywheel.
A separate class of chainsaws uses gasoline engines as their power unit. They are necessarily equipped with an ignition system responsible for the timely ignition of fuel-air consistency in the cylinders by means of electronic discharge, penetrating the spot between the electrodes. The correctness of the engine work depends on the moment when the spark appears. To check the technical condition of the ignition system of the purchased gasoline saw should be paid increased attention. How to check the ignition coil? In specialized stores, the equipment is sold in a workable form, but if the adjustment turned out to be knocked down, you can set the ignition on the chainsaw without the help of others.
Construction and operating principle of chainsaw ignition system
The standard ignition system of a carburetor engine consists of:
The magneto is a type of alternator which supplies the spark plugs with electrical energy. A simple way to check if with a working magneto on the magneto (it’s a who’s how. It consists of a fixed coil winding and a permanent magnet attached to the flywheel, which rotates with the crankshaft of the gasoline engine. The moving magnetic field produces an electromotive force in the low voltage winding, which is converted by the transformer into a voltage with sufficient potential to generate a spark.
Contact magnetos have the first lead of the high-voltage coil connected to the spark plug and the second lead through a mechanical switch to the earth. At a certain point, a special design element bifurcates the contacts, which leads to a sharp increase in voltage in the mains and a jump of spark in the interelectrode space of the spark plug.
To prevent overheating and oxidation of the chopper contacts, a capacitor is connected to the circuit.