Stihl chainsaw running full on in a cut. The stupid spark plug wire falls off. Now no spark. Have not checked anything yet, but thinking the coil is damaged by arc over.
Chainsaw coil damaged by spark plug wire falling off?
- Thread starter Exhaustgases
- Start date
Pic of what, its just a chainsaw, lots of pics online. The boot for the plug wire just came off the spark plug while running, so all that power had to go some place. Maybe internal arcing in coil? I don't know, just no spark now.
Does it have solid state ignition? Could have damaged the module, and if it's an older Stihl saw, they're pretty much unobtanium... Don't ask how I know... 
Have a tough time believing that, since the whole point is to arc over.
Maybe the insulation failed elsewhere, jumping from a break in the insulation. Remove the plug, hold onto the wire and give a good pull, that should be a good test of the coil.
Did you try a new plug? Might as well check the on/off switch, maybe the wire fell off.
Maybe the insulation failed elsewhere, jumping from a break in the insulation. Remove the plug, hold onto the wire and give a good pull, that should be a good test of the coil.
Did you try a new plug? Might as well check the on/off switch, maybe the wire fell off.
+1
Check the plug wire inside the boot and make sure it is still making contact with the coil wire.
I had a larger Stihl weed trimmer that developed a troublesome plug boot that would pop off occasionally. The coil was never damaged.
In the general motors SET "Specialized Electronic Training" i seem to recall distributorless ignition systems should never be ran without a spark plug or spark tester, however in real life people do it and get away with it.
If the coil really did fail, it would have failed anyways and was already on its way out. Having a plug wire fall off will not just fry a coil.
If the coil really did fail, it would have failed anyways and was already on its way out. Having a plug wire fall off will not just fry a coil.
It has fallen off a few other times with no problem plugging back on and starting. This time no go. How can it be a bad spark plug it was running top notch before this deal? Yeah unobtainium stihl ignition module, that is why I had to use one of those little after market ones years ago, it worked just great till now. I'll dig into it when I can. I should have dealt with the bad fit on the plug in the first place, it would have been less work and likely cheaper.
- Joined
- Dec 7, 2022
- Messages
- 30
Stihl is a good saw when they are running. I have a 250 and 390. Some of these coils have a spike sticking out and it stabs into the plug wire. You can use any old plug wire cut to length. If you use a screwdriver in the end or bolt etc held above the frame make sure you give it a hard pull or you wont see any spark. Good luck.
Whenever an ignition coil secondary is open circuited, it will attempt to generate the highest HT voltage it's capable of and that will usually be very much higher and possibly double or more than the normal voltage when the spark plug is connected. It stands to reason that this will stress the insulation on the secondary windings and can result in coil failure. On old points ignitions I've gotten away with it at low cranking voltages, but open circuiting at high speed is liable to cause more damage.
So you already replaced the coil with an aftermarket becuase the stihl was unavail, or too expensive?
This is one reason why stihl is my #3 pick for ownership. #1 - Echo, #2 - Husqvarna, #3 - Stihl. Echo has started obsoleting stuff from the 1980's and into maybe the mid 90s on certain products, husky gives you about 15-20 yrs tops before stuff becomes obsolete, but it usually is not a high failure part, however stihl really sticks it to their owners hard. They made some really awsome products only to intentionally obsolete a very critical failure part. Quite often after just 10 yrs. I do not support those types of companies with my money. An ignition coil should never become obsolete.
This is one reason why stihl is my #3 pick for ownership. #1 - Echo, #2 - Husqvarna, #3 - Stihl. Echo has started obsoleting stuff from the 1980's and into maybe the mid 90s on certain products, husky gives you about 15-20 yrs tops before stuff becomes obsolete, but it usually is not a high failure part, however stihl really sticks it to their owners hard. They made some really awsome products only to intentionally obsolete a very critical failure part. Quite often after just 10 yrs. I do not support those types of companies with my money. An ignition coil should never become obsolete.
Yup, Stihl is pretty low on my list to own, both for their current quality and parts availability. Some of the older parts they do have are so expensive you could buy a new piece of equipment for the price. It's sad because they used to make awesome stuff.
I agree with you that Echo is #1, Husqvarna is a close #2.
A new Nova unit fixed it. So coil is ok. Now for the other issues with it, like trigger spring.
This has the coiled wire type connector inside the boot and it just easily slips on and off. I will be replacing it with something that locks on very tight. Will have zero problems then.
I had a customer push mower with that issue. Every time you went over a bump the plug wire fell out just enough to not make contact and the mower would shut off. I love telling customers it was a no parts required fix.
When the wire falls off the transistor switch sees a voltage spike,. I am using power of tens for easy arthmetic, the actuall raitos and ovoltages are different. If the coil has a 100 to one turns ratio, if the plug takes 10K to fire the transistor sees 1000 volts. If the wire falls off, it sees much more voltage than normal If the protection circuits fail it can kill or reduce the life of the ignition. This does happen. Aftermarket GM ingition modules used to be touchy,
Rod
Similar threads
