Need Help From The Stihl Experts

[gtor72]

Hi all, I am in need of some opinions on this here stihl chainsaw.
It is a model 041AVFB, serial 112506059. (i know the ignition is different depending on serial number.)
It was brought to me to fix and i usually don't have any problem fixing these things. this one had rotten fuel lines so i thought simple fix...checked it for spark before doing anything.
So i now have it all back together after new carb kit and fuel lines.
This thing just won't fire, it won't even pop once.
It has 150psi compression with 3 pulls, it has spark, but to me it doesn't seem as strong as it should be.
Pouring a few drops of mixed gas into the carb does nothing, i have tried a little starting fluid (very little)
I am thinking i have a bad coil. everytime i pull the plug out it is wet.
the exhaust isn't restricted. i pulled the screen out and it was clean.
anyone have any other ideas, or do you think it is a bad coil?
thanks for any input or ideas you have. Mike

 

[Lakeside53]

you might just have a crankcase full of old mix.. take out the plug, tip it up on end and pull over (ignition off) until it stops draining out. Dry off the plug and try again.

Break the ground electrode off an old plug. If it jumps that gap, the coil is fine.

 

[litefoot]

break the ground electrode off an old plug. If it jumps that gap, the coil is fine.

Lakester,
Maybe I'm having a brain cramp, but can you elaborate on that one? If you break off the ground electrode, what gap are you referring to? Thanks.

 

[Lakeside53]

The gap between the center electrode and the threaded base... Forcing the coil to work at a higher voltage by increasing the gap simulated the voltage needed to fire at 10 bar.

 

[belgian]

I worked on an 041AV last week and couldn't get it to run either, untill I found that some idiot who worked on it before reversed the connections to the fuel and impulse inlet on the carb, grrrrrrrr....

but since your plug is getting wet, it should be an ignition problem imo.
I suppose you tried another plug already.

 

[gtor72]

yes i have tried a different spark plug. will try the electrode trick that lake suggested.
the spark seems weak to me. thanks, will let you know what i find tonight. Mike

 

[litefoot]

The gap between the center electrode and the threaded base... Forcing the coil to work at a higher voltage by increasing the gap simulated the voltage needed to fire at 10 bar.

Gotcha! Sorry, head was in patooty. Thanks.

 

[gtor72]

some test results

thanks for all the responses so far, i sat the saw up on end overnight and no excess fuel drained out the spark plug hole.
i have a book that has two tests for the coil here are the results i came up with, let me know if they make sense to you stihl guys.
one is to test primary wire to ground should be 0.4-0.5 ohms, i have 0.2,
second is plug wire to ground, should be 2700-3300 ohms, i have 1950.
Does it sound like a bad coil to you? thanks in advance for any further help. Mike

 

[Lakeside53]

The best test for a coil is simply to do as I suggest - see if it can spark across a large gap. Ohm measurements are often wrong as coils change and service manual don't.

 

[galde]

041 won't fire

check the spark timing.

 

[PES+]

Galde might have it

If someone already worked on the saw it may have mismatched ignition components.

Hard to say from you static DC ohm readings with any certainty as your meter may be off that far......particularly in the low ohm range.

Lake's suggestion is the best way to tell for sure that the coil is up to snuff. IF that checks out you need to check when the spark is occurring.

 

[andrethegiant70]

One of the things you should consider (has already been alluded to) is that the timing is off. Check that the keyway on the crankshaft is present and not sheared. You'll need to remove the flywheel. One of the Stihl guys will have to talk you through that. I've not done it on an 041.

If this saw is in decent nick, these troubles are worth going through. There is probably not much wrong with this saw. Also, for giggles, make sure your intake stack is snug. The fact that the plug is wet means that it should probably pop (at least), but these saws are notorious for this and ya never know.

 

[Al Smith]

Don't forget to check the air gap on the coil.Too far away,it won't fire at cranking speed.Simple but often overlooked.

 

[Lakeside53]

yes... just use a business card - loosen the coil, insert card, rotate until both coil arms are on the magnets, tighten screws.


Sheared flywheel key on an 041? Never seen one ever.. possible, but very rare..

 

[gtor72]

thanks for all the suggestions i really appreciate it,
i do not have a sheared flywheel key, it is ok.
The spark will not jump on the plug as lakeside suggested, i also have one of those spark testers that is adjustable to see how far it will spark, it won't spark more than a 1/16 of an inch.
this saw has whats called an SEM igniton according to my book.
how would you go about adjusting the flywheel gap when all the components are under the flywheel?
or do you think now i have a bad coil or ignition components?
thanks again, Mike

 

[Lakeside53]

Oh,, you have one of those

To adjust any gap, you need to remove the flywheel and either make or scrounge a test flywheel that's been cut away..

If you have an SEM electronic module (on a FB?) , then that's your problem. You can't buy them new... and be careful with used unless the seller guarantees it.

Look carefuly at your flywheel. If the magnets have any cracks, then that could be the problem.

 

[PES+]

Are you SURE it's an 041?

Sounds pretty strange.

I have complete ignitions with flywheel to change it out.

I probably have the SEM units too but people are getting shy about them.

 

[gtor72]

yes i'm pretty certain it is an 041.
Its a pretty clean well taken care of saw.
It still has the decal on the air filter cover and it says 041AV Electronic quick stop farm boss.
how much would the ignition parts cost me?
you can send me a pm if you like. zip is 49305. thanks archie, also will be looking for that jonsered 625/630 piston and crank seals as soon as i get back into that project and make sure which saw it is that i have. thanks again all. Mike

 

[gtor72]

yes i'm pretty certain it is an 041.
Its a pretty clean well taken care of saw.
It still has the decal on the air filter cover and it says 041AV Electronic quick stop farm boss.
how much would the ignition parts cost me?
you can send me a pm if you like. zip is 49305. thanks archie, also will be looking for that jonsered 625/630 piston and crank seals as soon as i get back into that project and make sure which saw it is that i have. thanks again all. Mike

 

[PES+]

I'll dig into the 041s sat or next week

I'll let you know what we have for options.

I could be mistaken but I don't recall there being any gap adjustment on either of the Stihl internal electronic coils, only timing adjustment.