The Undying 025

[Sam R]

I've got an 025 in the shop now, that I've worked on in the past. Customer brought it in wanting me to replace the module. He brought his own non-OEM module; just wanted it swapped. I don't remember asking him how he knew the coil was smoked, or even if I tested it. I stay busy enough that if someone comes to me already decided on what it needs AND brings the part I'm going to do just what they want and get paid.

That said, I can not get this damn saw to shut off. The new coil works so well that there's no way to stop it without choking it or pulling the plug wire.

I've tried a new AM Stens module as well, it has the same problem. I've checked continuity on the ground wire & the shut off wire. all good there. I tried just bypassing the shut off wire with a piece of wire on the module & alligator clips to the ground wire... It sparked a bit but wouldn't shut off.

So I'd like some ideas. OEM coils for the 025 are about $95 retail and he's not interested in spending that much on it, I don't think. Also, like to add the air gap is set correctly. My only theory is that the voltage in the module is somehow out of wack with what the ground can overcome to shut the saw off - which may mean OEM is what it'll take.

Have any of you encountered such a problem before? What was the solution?

 

[HarleyT]

Jumper wire hooked up?
Here is an old junker....

 

[Sam R]

Jumper wire hooked up?
Here is an old junker....

View attachment 742429

Being the one from the coil to the multifunction lever? Yes, tried it that way, also tried bypassing that with a heavier gauge wire to see if there was some transmission problem and it didn't work.

 

[dmb2613]

make sure you have the wire from the coil to the cylinder hooked up, it has to be to work

 

[CausticUC]

Does it idle properly?
Trying to recall if this saw has two magnets or not.

 

[CausticUC]

Reason I ask is that I've only once had a similar type behaviour and it was not on a saw.

The engine was double sparking close together, initially the engine idled fine. After a little while it would start being unstable until it backfired or preignited violently.

 

[Sam R]

It idles and otherwise runs perfectly. As far as I know the 025 is a single magnet set up but I don't really remember checking whether it was.
I haven't ran it that long really just started it and revved it up to see how it was going and it seemed to run great. Just couldn't switch it off!

 

[a. palmer jr.]

It sounds like to me that the ground wire in the coil is not connected. It's grounded on the outside of the coil but not in the coil where it needs to be to kill the spark..

 

[CausticUC]

It sounds like to me that the ground wire in the coil is not connected. It's grounded on the outside of the coil but not in the coil where it needs to be to kill the spark..

In my case, it did turn out to be an intermittent connection. Actually there was a broken ground wire inside the sheath.

Never had it happen again. Nothing worse than a runaway engine where you are suddenly confronted with the puzzle of how to shut it off!

 

[a. palmer jr.]

I've had two or three in all the time I've worked on saws, just a broken wire inside the coil and I assume can't be repaired other than another coil..

 

[Sam R]

I've had two or three in all the time I've worked on saws, just a broken wire inside the coil and I assume can't be repaired other than another coil..

That's what I was kind of wondering, but I've used 2 coils on it now. Neither of them OEM, but one was Stens which is a reputable AM brand.

 

[dmb2613]

Being the one from the coil to the multifunction lever? Yes, tried it that way, also tried bypassing that with a heavier gauge wire to see if there was some transmission problem and it didn't work.

make sure you have the wire from the coil to the cylinder hooked up, it has to be to work

Did you read my post?

 

[L34]

Test from the kill wire terminal to the coil core with a multimeter.
Should be 0.1 to 0.2 ohms.
If it's open circuit theres your problem.
Kill wire terminal not connected to coil primary winding.

 

[a. palmer jr.]

If you have a continuity meter you can check to make sure the grounding circuit is complete and connected at the switch, other than the grounding circuit it has to be the coil. Some engines have a hot spot in the combustion chamber that allow an engine to run even if there's no ignition but don't know it that's the case here. In that rare occasion you'd have to tear it down and clean the carbon out of the combustion chamber and look for any little spots in there that might form a "glow plug" but the engine would also have to have high compression and run a bit lean...

 

[Sam R]

Palmer I don't think it's a hot spot. I suppose it could be, but I've worked on this saw before - it's in pretty good shape, and the last time it was in the shop 6 months ago it was running perfectly.

Did you read my post?

Yes, sorry I didn't reply directly - I suppose the basics have to be seen to after all - the wiring is connected correctly.

Test from the kill wire terminal to the coil core with a multimeter.
Should be 0.1 to 0.2 ohms.
If it's open circuit theres your problem.
Kill wire terminal not connected to coil primary winding.

My MM is pretty low quality, it reads all wires at about .8 ohms, and I checked on a couple known good connections. That's what the wiring on the 025 was reading at, and the bypass wire I'd hooked up, too. And when you put it in the "0" position it reads infinite like it should. I'm really starting to think the problem is the module.

Also like to add that I'd cleaned the connection on the ground wire to the cylinder & where the coil & ground wire connect, to rule that out.

 

[L34]

Not talking about any wiring or switch on saw.
Just the terminal on the coil to the coil core or cylinder with wire removed from terminal.
All the wring and switch may be good,but if the terminal is not connected internally to the coil
primary winding the saw wont stop.
If your MM reads .8 with leads shorted then go with that reading,should be .8-1 ohm
by your meter.

 

[a. palmer jr.]

I'm thinking it is the coil also. If the external connections are grounded then the internal connection must be open...

 

[CausticUC]

Would not get too hung up on actual values at that range, it is a continuity check you are doing. Values will deceive you if it is a broken wire and the jacket is heat expanding at the break.

This might be a good situation to use an inline spark tester and watch what the spark is doing when you try to kill. If it is not a wire issue, I'd be wondering if there is a capacitor or condenser still hooked up that is storing enough charge to defeat the kill.

 

[HarleyT]

If grouning out the coil at the terminal doesn't shut the saw off, then it is in the coil.

= New coil.....

 

[CausticUC]

If grouning out the coil at the terminal doesn't shut the saw off, then it is in the coil.

= New coil.....

Now that you mention it, he should be able to start the saw with the switch off.

Going oldschool, could run a kill wire from under the plug to the switch or hanging out to manually ground for the kill. (Good old Briggs.... funny how they used to do that)