025 coil bad?

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

vegaome

ArboristSite Operative
Joined
Jun 20, 2006
Messages
387
Reaction score
86
Location
Cider Run, WV
Howdy Folks,

I had two 025 that I was working on today. !st was clean sharpen and adjust, cut a few pieces, good saw. 2nd one was my brother's, he said it would run for a while then would not restart. I had already replaced the feul line because I could see the cracks in it and the impulse line (old one was good after I got to it but replaced it anyway) and both diaphrams in the carb. I did all the normal maintenance stuff on it, dress bar, sharpened chain, cleaned air filter, new plug and did a good cleaning on the saw.

It would start and I let her warm up and she didn't sound right and wouldn't idle right. I was chasing the idle but just couldn't catch it so I shut her down and seated the L screw and backed her out one turn. I go to restart and she wouldn't fire. Plug was wet but no spark. Took it back to trailer/shop and busted out the multi meter. Measured resistance from plug wire to short circuit terminal on coil and it reads 6.5Kohms, measured from short circuit terminal to ground and it reads 5.7Kohms.

I pulled the cover off the other (good/working) 025 and measure resistance from plug wire to short circuit terminal it reads 10.7Kohms, measured from short circuit terminal to ground and it reads 1.6 ohms.

So I believe the coil is bad. Before I tell him to take it to the dealer is there anything I'm missing? It may be under warranty so I don't want to pull the plug wire out or mess up anything (afraid the dealer might tell him he won't cover it because you monkeyed with it). I will only do nondestructive type stuff for the moment. I do want to see if I/he can keep the old coil so I can take it apart and see whats in there.

Have a good evening all.

v/r

Mike
 
Measurements with a multimeter are often not conclusive on these ignitions - you aren't measuring the actual coil winding - there is electronics in the way...

Best test is spark - pull off the coil shutoff wire (to make sure here is no problem outside the coil, connect a plug to the boot, ground the plug body to the cylinder (use a big battery clip or whatever to clamp the wire to the plug body, pull up the center electrode to make a wide gap (simulates the extra voltage required to fire under pressure), and pull way... NO spark, usually bad coil... but there is still a tiny change your ignition lead is bad. I assume the ground strap from the coil to the engine is intact?
 
This is a test

Have you checked the spark with a spark tester or at least a plug gapped very wide?
You may very well be right, but the spark test is my first step. The ohmmeter test I do on the switch and ground wires to check for shorts and opens.
 
Measurements with a multimeter are often not conclusive on these ignitions - you aren't measuring the actual coil winding - there is electronics in the way...

Best test is spark - pull off the coil shutoff wire (to make sure here is no problem outside the coil, connect a plug to the boot, ground the plug body to the cylinder (use a big battery clip or whatever to clamp the wire to the plug body, pull up the center electrode to make a wide gap (simulates the extra voltage required to fire under pressure), and pull way... NO spark, usually bad coil... but there is still a tiny change your ignition lead is bad. I assume the ground strap from the coil to the engine is intact?

Howdy Lakeside,

Yes the ground strap is intact and all the wiring looks good. Grounds all working as is the kill switch, checked all that with the meter and I did the spark test as you described with the shutoff wire disconnected. The only thing I did not do was open up the gap (good idea there). I did check the plug in the other 025 and it worked ok there. It has been sitting for a couple of hours so I may go back out and tinker with it.

I did notice that the two saws have different coils. But as far as I know my brothers is pre 2003, the other is somewhere close to or after 2003. Both are original owners and no high dollar parts ever replaced.

Lake whats in there? IC chip?

Thanks for the help Andy.

v/r

Mike
 
There a handful of resistors, couple of diodes, an scr... you'll not see much though... it's all potted in epoxy. I'll try to dig up a photo of the non-encapsulated stuff.
 
Howdy Stihltech,

I hope you don't think I was ignoring you. I must of been typing my other reply and it took me so long that I missed your reply. Yes I did do a spark check out in the woods and then again back in the trailer. I did check for open and shorts to. Everything is good except I fear the coil. My brother called and I told him the news. Not sure but I think it may be covered under the warranty.

Howdy Again Lakeside,

I hate to say it Andy but if thats all that is in there, the epoxy probably costs more than the parts to make it. Stihl is standing behind the customer with both hands on our shoulders (as someone mentioned before), when it comes to parts. I would love to see a photo of it before the epoxy.

Have a good one fella's.

v/r

Mike
 
Wiring Diagram

I'm putting back together a 250 and can't remember how the stupid wires go. I know, I should have taken a picture of it. It looks like there is one jumper taht goes from teh coil mount to the jug. Can somebody give me the lo-down or post a photo?

Thanks!

Robert:sucks: :chainsawguy:
 
Just a little aside here, the last time you fellas helped me with an 025 spark, it was the PLUG that was bad. Now I'm looking for an extra 025 to go with my extra coil! (Gettin' a little tired of wiping egg off my face!)

Just be sure to check everything before you spend money on a coil.
 
I am sure the previous posting guys have hit the nail on the head,but one experience I have recently had with "No Spark" on an 066.
Whilst building one up from donor saws,I couldn't get any spark,even with trying three different coils.
In the end,I replaced the Poly Flywheel (identical part #'s) and I had SPARK.
Tried all 3 coils. All coils sparked.
Swapped out flywheel,back to first one. NO SPARK again.

So,tell me how does a flywheel lose its magnetism?
 
If the flywheel gets dropped it can not only loose magnestism, but reverse one or more of the poles. Rare, but it happens.
 
But what if you are south of the equator?



Just for fun, see if the polarity is the same on both flywheels, just use any old magnet to find out.
 

Latest posts

Back
Top