Compared to older points type of coils, modern electronic coils are having a higher failure rate and this is largely due to failure of the semiconductor components that replace the switching function of the points. Heat is the enemy of semiconductors and there is a range of quality in these devices, components have been developed to withstand the high temperatures that are required by some military specs but they are very expensive so I guess they aren't going to be used in the chainsaw industry anytime soon.
Can we do anything to help with the lifetime of our coils? Since heat is an issue, the coils should be kept as cool as possible. They are mounted where the air from the FW fan keeps them cool but often they get packed in with sawdust and crud that is a good insulator, so as part of regular maintenance, the starter cover should be removed and all the crud blown out from around the coil. Coils seldom fail while the saw is running, the usual story is that it was running fine when it was shut off and later it wouldn't start and had no spark. When the saw is shut off, the residual heat of the cylinder soaks into the coil and elevates its temperature with no air to cool it. If you have just finished some serious cutting with the engine running at full power, it is a good idea to let the saw idle for a few minutes to bring the temperature down before shutting it off. Might help. Some coil failures might be due to a fault in the secondary windings. When a spark event occurs, the secondary voltage rises to the point where it will arc across the plug gap and when the plug arcs the voltage will go no higher. If the secondary does not have an arc path to ground, the voltage will rise to the maximum that the system can produce and this may be enough to break down the thin insulation of the wires that the secondary is wound with, and this could eventually lead to a bad coil. To protect the coil, the engine should never be turned over fast with the ignition switch on and the plug lead off. If you have to do this, the plug lead should be shorted to ground, IT WON'T DAMAGE THE COIL.
None of these steps will guarantee that the coil won't fail, but they are easy to do and might help.
Can we do anything to help with the lifetime of our coils? Since heat is an issue, the coils should be kept as cool as possible. They are mounted where the air from the FW fan keeps them cool but often they get packed in with sawdust and crud that is a good insulator, so as part of regular maintenance, the starter cover should be removed and all the crud blown out from around the coil. Coils seldom fail while the saw is running, the usual story is that it was running fine when it was shut off and later it wouldn't start and had no spark. When the saw is shut off, the residual heat of the cylinder soaks into the coil and elevates its temperature with no air to cool it. If you have just finished some serious cutting with the engine running at full power, it is a good idea to let the saw idle for a few minutes to bring the temperature down before shutting it off. Might help. Some coil failures might be due to a fault in the secondary windings. When a spark event occurs, the secondary voltage rises to the point where it will arc across the plug gap and when the plug arcs the voltage will go no higher. If the secondary does not have an arc path to ground, the voltage will rise to the maximum that the system can produce and this may be enough to break down the thin insulation of the wires that the secondary is wound with, and this could eventually lead to a bad coil. To protect the coil, the engine should never be turned over fast with the ignition switch on and the plug lead off. If you have to do this, the plug lead should be shorted to ground, IT WON'T DAMAGE THE COIL.
None of these steps will guarantee that the coil won't fail, but they are easy to do and might help.
one picture says more than 1000 words
