How to check the ignition coil on the trimmer
The first way to check the ignition coil involves the use of special equipment (stand). It is not available at home. you can find it only in service centers.
Replacing breaker contacts
After disassembling the magneto, it is necessary to remove the old breaker contacts and install the new ones correctly. To accomplish this, you must:
- move the latch, remove the cover from the breaker;
- unscrew the screw holding the connecting wire;
- remove the screw securing the breaker plate to the magneto cover and remove it;
- get the screw securing the breaker spring;
- remove the lock washer from the axle, and then the lever with the cushion assembly, which it holds;
- unscrew the screw securing the contact post, remove the part from the axle.
Assemble the assembly with new contacts in the reverse order.
On a note! Despite the ease of operation, most often trimmer owners prefer to simply replace the magneto with a new one.
How to Check the Ignition on an Echo SRM 225 String Trimmer
Typical problems. causes
The malfunctions that most often occur with magneto are typical for trimmers from different manufacturers. As a rule, this is a weak spark or its absence, as well as the presence of interruptions in this process.
If the magneto sparks intermittently, the contacts must be checked first. They could be burnt or oily. The carbon deposits found are cleaned with a file, and the oil is wiped off with suede, previously soaked in gasoline. The second possible cause of the problem is the adjustment of the gap between the contacts. To eliminate it, you need to set the correct distance.
If the spark is intermittent, it could also mean that the breaker arm pad is worn out. To eliminate the malfunction, you must change the lever to a new one. In addition, the clearance should be adjusted, as with another possible cause of breakdown. misalignment of the outline.
Capacitor breakdown can also be the culprit for interruptions in spark formation. In such a situation, replacement of the damaged part is required, since it cannot be repaired and recharged.
If there is no multimeter, you can check the coil in another way.
Ignition Coil Primary & Secondary Resistance Testing
Important! Check carefully so that the magneto does not burn out. For this, it is important not to touch the cylinder with the electrode.
To diagnose, you need to take the following steps:
- open the cover that covers the cylinder;
- remove the cap of the high-voltage wire from the candle without unscrewing the part itself to maintain compression;
- tightly place a nail without a cap in the cap, it will simulate the central electrode of the candle;
- tie the cap with a nail to the cylinder with a dielectric material so that the gap between the simulator of the candle electrode and the mass ranges from 5.5 to 7 mm (the exact distance for a particular model is recommended to be found in the user manual), but the part does not come into contact with the mass;
- using the starter to reproduce the engine start several times, holding the ignition button in the on position;
- if a spark appears, you need to consider what color it is.
A strong white or bluish spark is normal, and a faint flash of orange or yellow indicates coil failure.
Testing and replacing the ignition coil on a Stihl FS 80R string trimmer
Often, a cold magneto creates a powerful spark, but when heated, due to a defect in its internal components, it does not conduct current. After the coil has cooled, the mower starts up again and mows the grass with a line or knife until the magneto heats up. This is abnormal behavior and the coil must be changed.
On a note! In a similar way, the problem can manifest itself when the candle heats up and cools down, so it is recommended to check the performance of both parts.
Grass trimmer ignition coil. faults and repairs
Brushcutters are a popular seasonal tool designed to remove unwanted vegetation from your home. Like any other technique, these devices break down periodically. Grass trimmer ignition coil repair is one of the popular problems with gasoline scythes. The ignition system itself is designed in the same way on two- and four-stroke internal combustion engines, so the elimination of breakdowns is performed almost the same for tools from different manufacturers, be it Lux, Huter, Husqvarna or another brand. Methods for restoring the performance of the ignition coil or replacing it with a new one. in the material below.
Magneto. design and operating principle
The purpose of the ignition coil is to convert the rotational energy into a high-voltage discharge and form a spark that ignites the fuel mixture. In an internal combustion engine, this part is called a magneto, since in it an alternating current is generated from the rotation of a permanent magnetic rotor or armature.
Magneto structurally consists of two windings: high and low voltage. A capacitor with breaker contacts is connected in parallel to the latter. Whereas the leads of the high voltage winding are connected to the candle and the body. They are both wound on a core, between the poles of which a rotating magnet is installed, magnetized longitudinally.
On a note! The whole structure looks like a large coil mounted on a U-shaped core.
How to check the health of a magneto
Magneto is the main part of the engine ignition system and is a coil with primary and secondary windings located around the core. Often, due to a malfunction of the magneto, the spark on the spark plug disappears and the fuel does not ignite. To check the coil, you need to use a tester, and follow these steps.
- On the tester, after switching to the resistance measurement mode, you need to set 200 ohms. In this way, the primary winding will be checked.
- Connect one electrode of the tester to coil ground and the other to the lead coming out of the magneto. Normally, the resistance should be between 0.4 and 2 ohms.
- To check the secondary winding, you will need to set the device switch to 20 ohms. Further, one probe of the device is inserted into the candle cap, and the second is connected to the “mass”. Normally, resistance indicators should be in the range from 4-6 kOhm and above (depending on the model).
When the circuit is open, the device will show infinity, and when closed. 0 (zero).
If you do not have a tester, then you can use the following method, being very careful so that the electrode does not touch the cylinder, otherwise the coil will burn out.
- Remove the cap from the candle. You do not need to unscrew the candle in order to maintain compression.
- It is necessary to insert a nail without a cap into the cap. The nail should be of such a diameter that it adheres well to the cap.
- Tie the cap with the nail to the cylinder using a dielectric so that the gap between the electrode and the cylinder body is between 5.5 and 7 mm (but in no case touches the “mass”).
- Using the starter, simulate the engine start several times. The ignition button must be on.
- Observe if a spark appears and what color it has.
Normally, the spark should be strong, white or bluish. If the spark is weak, and its color is orange or yellow, this indicates a faulty magneto.
You should also consider the fact that sometimes cold magneto can give a good spark. But after heating, due to internal malfunctions, it ceases to produce current. As soon as the coil cools down, the grass trimmer starts up again and runs for a while until the magneto warms up again. This coil needs to be replaced.
Sometimes a spark plug can cause a similar heating problem even if the coil is OK, so both parts need to be checked.
Trimmer ignition setting
On gasoline trimmers, both two-stroke internal combustion engines (ICE) and four-stroke engines are used. But the ignition system in them is no different from each other, therefore, the repair and adjustment of this fuel ignition system will be the same for different types of internal combustion engines.
Why do I need ignition adjustment
In some cases, when the engine does not start, the ignition will need to be adjusted. Of course, first you need to check the condition of the candle and the high-voltage cable with a cap.
It is necessary to adjust the ignition on a two-stroke engine in order to ensure timely ignition of the fuel in the engine combustion chamber. Below is a diagram from which you can understand the principle of operation of the internal combustion engine.
The spark in the spark plug should appear at the moment the fuel is compressed by the piston, when it does not even reach the top dead center (TDC). When the piston passes TDC, the fuel mixture ignites, as a result of which the piston goes down under the action of the explosion energy.
Therefore, if for some reason (mainly due to the displacement of the flywheel on the shaft relative to its original position), the fuel ignites before the piston passes TDC, then it goes back, and the crankshaft rotates in the opposite direction. This movement can damage the starter assembly, cut the starter cord, etc. In this case, early ignition of the fuel occurs.
There may also be a late ignition on the trim: the piston, after compression of the fuel that has not ignited, goes down, and at this moment a spark appears. In this case, the engine will either not start, or it will significantly lose power and it will be bad to gain speed.
But such problems with early or late ignition on two-stroke internal combustion engines are quite rare, since the flywheel with magnets is already installed in the correct position, which is perfectly synchronized with the movement of the piston. In addition, the flywheel is secured to the shaft with a key and nut. Therefore, incorrect installation of the part is excluded.
Basically, ignition adjustment is about setting the correct gap between the magneto and the flywheel.
How the trimmer ignition system works
The ignition system of a two-stroke internal combustion engine consists of 2 elements: a flywheel and a coil (magneto). The picture below shows how they look.
The flywheel has an impeller that acts as a fan to cool the engine. Also on one side of the flywheel are permanent magnets, shown in the figure by an arrow.
When the flywheel rotates, an electric current is generated in the coil, which serves to produce a spark on the spark plug. A spark appears when the magnets are directly below the magneto.
Ignition adjustment algorithm
Trimmer ignition is quite simple to adjust.
Remove the engine cover from the engine by unscrewing all the bolts holding it. For example, on a Patriot (Patriot) PT 2540 petrol cutter, to remove the cover, you will need to unscrew the air filter housing, and remove it from the latches with a flat screwdriver. After that, the plastic case can be easily removed.