Oem coil vs aftermarket coils

[IntegrityCarpentry]

So the spark plug connector came off my 272xp. It was an aftermarket coil I bought in 2019. I have had my problems with aftermarket parts. I am wondering if my coil is working fine is it going to work for a while, do aftermarket coils either work or not? Or do the oem coils ProForm better in all areas and it’s just worth it for them? Are there differences in output? (Stronger spark etc)
I don’t like to have problems that I can prevent. Pretty much all the wear items have now been replaced in this saw and I was hoping I could use it for a few years.
I can A. Put a better oregon or other connector on, this cheap one was destined to fail.
B. Get a Taiwanese coil instead of Chinese
C. Get a new oem one

Just about all I know about saws I have learned working on this saw. So I don’t know a lot. Thanks for the advice!
Gabriel

 

[J D]

D. Re-attach connector to wire, fit boot with a bit of RTV to retain it.
Worry about replacing it if it actually gives problems in the future... by which time you may have had the opportunity to acquire a replacement

 

[Mad Professor]

Used OEM

 

[bwalker]

I've never had good luck with aftermarket coils. However I've only used them on Lawnboy mowers snd Toro Snowblowers, both of which eat coils.

 

[IntegrityCarpentry]

I've never had good luck with aftermarket coils. However I've only used them on Lawnboy mowers snd Toro Snowblowers, both of which eat coils.

Thank you, I am real thankful in that case my toro snowblower is still running. So I am now prepared on snowblower, do coils fail completely or do they start working sporadically and then fully fail?

 

[huskihl]

I have tested a few with a timing light and the aftermarket coils fired a few degrees later than OEM. If yours has lasted since 2019 and you’re happy with it, I would fix the end and keep running it.

 

[bwalker]

Thank you, I am real thankful in that case my toro snowblower is still running. So I am now prepared on snowblower, do coils fail completely or do they start working sporadically and then fully fail?

They just stop working. I actually have one failed right now. I had the machine pulled apart this winter because the recoil rope broke. When I got it back together I found the coil had failed...while sitting!

 

[Old2stroke]

Most common problem I have had with AM coils is the timing curve is not correct. Usually too far retarded.

 

[SteveSr]

I wouldn't trust AM. The Stihl coils as of a decade or two ago all had PIC micro-controllers in them. The micro controlled the advance curve. Doubt that the AM is anywhere near as sophisticated.

 

[Mad Professor]

I wouldn't trust AM. The Stihl coils as of a decade or two ago all had PIC micro-controllers in them. The micro controlled the advance curve. Doubt that the AM is anywhere near as sophisticated.

Stihl used to have lifetime warranty.

 

[IntegrityCarpentry]

D. Re-attach connector to wire, fit boot with a bit of RTV to retain it.
Worry about replacing it if it actually gives problems in the future... by which time you may have had the opportunity to acquire a replacement

Sounds like a good plan, thanks, minus reusing old connector, it didn’t work, so I need to find one also.

They just stop working. I actually have one failed right now. I had the machine pulled apart this winter because the recoil rope broke. When I got it back together I found the coil had failed...while sitting!

oh joy…. I should get a spare coil then for it. Thank you for your advice in advance

 

[IntegrityCarpentry]

I have tested a few with a timing light and the aftermarket coils fired a few degrees later than OEM. If yours has lasted since 2019 and you’re happy with it, I would fix the end and keep running it.

Well that tells me it was a good thing I ordered a new oem one this morning. The saw seems a touch off and I May keep old as a desperate xtra. Thanks for the info!! Just the stuff I was looking for!!

 

[J D]

Most common problem I have had with AM coils is the timing curve is not correct. Usually too far retarded.

Coils aren't the only aftermarket parts that can be excessively retarded
As mentioned OEM is best... used if the budget doesn't stretch to new.
Coils will sometimes become intermittent or fail as they get warm & then function again once they've cooled down

 

[SteveSr]

Coils will sometimes become intermittent or fail as they get warm & then function again once they've cooled down

I have seen this happen too often with Walbro manufactured modules for the Stihl 4137 series (FS-75, 80, 85, etc).

 

[IntegrityCarpentry]

I have seen this happen too often with Walbro manufactured modules for the Stihl 4137 series (FS-75, 80, 85, etc).

Thank you. I might have one of those to watch now

 

[leaf]

I wouldn't trust AM. The Stihl coils as of a decade or two ago all had PIC micro-controllers in them. The micro controlled the advance curve. Doubt that the AM is anywhere near as sophisticated.

Whilst trying not just to "whine"... but coils are probably the most "obscure" / "opaque" / "black box" part of chainsaws. We -- the "general" we -- know the sizes of metal parts to the thousandth, and we have pretty elaborate specifications for synthetic 2-cycle mix oil, and a lot of details about chains and sharpening, but I don't know anybody who knows... for example, the manufacturer specified timing or "timing curve" (relationship with RPM) for any of his or her chainsaws, nor has a schematic diagram for the electrical / electronic "contents" of the black epoxy "block" from which the plug wire emerges, nor has a secondary voltage specification, etc. etc.

So come my (stupid) questions: 1. How did you happen to find out that Stihl has PIC micros in their coil assemblies? 8 bit? How do they handle power management? Charge a capacitor and then have a semiconductor regulator? Do they use them as digital count timers? 2. Can you -- anybody -- figure out a way to force the manufacturers to disclose what is actually in the black epoxy block? Can anybody figure out how to make the manufacturers produce an ignition specification (secondary voltage / timing at RPM, etc) for each saw? 3. Does anybody happen to have something other than 'anecdotal' information about chainsaw coil failure rates? (My -- very limited -- experience is that there are some coils that just keep going, but others that fail, sometimes without a lots of use, or heat or... and that many chainsaw users I know do not recognize that a coil has failed when in fact it clearly has -- just "this saw doesn't start...") And, for what it might or might not be worth, my very limited experience does not suggest that aftermarket coils are any worse or better than OEM; it in instead that some coils of either sort have a propensity to fail, and others don't, but otherwise the only guide is the failure of other coils of the same type....

 

[pioneerguy600]

The modules are not actually serviceable so knowing all the specifics of componets used in manufacture and all specifics to timing curves, retard or advance are rather moot, since they are totally sealed units they are a replacement item in chainsaw repair. Have at it digging one apart,identifying components and finding replacements let alone trying to reinstall them. Definitely not cost effective for any repair shops.

 

[leaf]

Oh no, I have no thought of successfully "disassembling" a saw ignition module. But I'm not sure that having electrical "specifications" for chainsaw ignitions is a waste of time. Indeed, the total impracticality of getting "into" a module is one reason I vote for disclosure. It is possible to "observe" chainsaw ignition by taking the chain off, putting the bar in a vise, attaching a pickup to the plug wire and a "degree wheel" (of various forms) to the open clutch side. Depending on the pickup it is also possible to get a useful measure of secondary voltage, etc.

The motives are several: 1. Fixing individual saws. (Some module is brand new, put on a saw, and its sorta starts, but you've got to pull super fast at the cord to get it to go. Is it not making spark until it gets spun faster than usual pull? What does it owe you at what speed?) 2. Developing a kind of "community" consensus and understanding. One set of saws shows ... 18kv on the plug wire (at pull on the cord), another is characteristically 12 kv -- and has a tendency to foul. Worth knowing -- and even maybe having an opinion about. 3. There are people pushing ignition advance -- which is fine -- but they are a bit too much at the mercy of "cut and try" (and somewhat "get lucky") methods. Figuring out that Q degrees of advance is good, and Q+ really isn't -- is worth it to them.

So. No worries. We've all got a lot of ignition modules that do a lot of workiing -- and which we might as well just not worry about. But, I do continue to think that knowing about modules, rather than not knowing is, in its own way, gooder.

 

[pioneerguy600]

I have only been working on saws and engines a short time, since 1964 and have yet to be able to return any electrical component to a dealer, once purchased it is yours is how they all work it around here so either the engine gets spark from a new module or not you own it. All the testing of coils or modules in the world will get me nowhere, if it works it works, if it don`t then it still needs replacement , how it works will not solve any issues but just knowing how it works never hurts, information is really no load to carry but wishing manufacturers would disclose how they work and what components are used in making them is just that, wishing and not much more.

 

[xraydaniel]

AM coils can be a bit troublesome for sure