Chainsaw coil question

[SkiWhiz]

I have a little McCullough MacCat chainsaw that I got running well, the issue is that it won't shut off with the kill switch. The wires going from the kill switch to the coil are good, the kill switch works as it should and the saw runs great. Is it possible that the coil is bad even though the saw runs.

 

[guysmiley]

test continuity of switch. should be open/closed and then check for case ground on one side of switch with coltmeter. Thats the easy place to start anywho.

 

[cscltd]

It is possible that coil is faulty. They can (but rare) work perfectly fine but will not ground out to stop.

 

[L34]

As above.
Have seen this.(once)
Wire broke internally in coil.
Multimeter proved this.

 

[SkiWhiz]

test continuity of switch. should be open/closed and then check for case ground on one side of switch with coltmeter. Thats the easy place to start anywho.

I checked the switch and wires to the coil for continuity and they checked out fine. I get .900k ohms on the primary and secondary so I think that it is bad but it runs fine that what doesn't make sense to me.

 

[pioneerguy600]

I checked the switch and wires to the coil for continuity and they checked out fine. I get .900k ohms on the primary and secondary so I think that it is bad but it runs fine that what doesn't make sense to me.

I checked the switch and wires to the coil for continuity and they checked out fine. I get .900k ohms on the primary and secondary so I think that it is bad but it runs fine that what doesn't make sense to me.

Likely just the internal connection that runs from the coil to the switch wire has failed, you can just remove the wire from the switch and ground it directly to the cylinder when the engine is running, if it does not shut the engine down then that circuit is broken.

 

[SkiWhiz]

Checked the wires to the switch for continuity, all good. Grounded kill wire to engine while running, did not stop it from running.

 

[ChuckMI]

I have a brushcutter on which the kill switch doesn't work, so I just turn it off with the choke. If it works well otherwise, why worry about it?

 

[SkiWhiz]

I was never a fan of choking an engine out to stop it, if I decide to sell it I want it 100%

 

[Gord404]

Had a 372 once that it was the coil

 

[stihltech]

Occasionally I get a coil that is disconnected internally.

 

[samaritan]

My Stihl ms251c did the same thing, I cleaned the two metal pieces that touch when you shut it off, that cured it

 

[SkiWhiz]

My Stihl ms251c did the same thing, I cleaned the two metal pieces that touch when you shut it off, that cured it

I ended up selling the saw the way it was and the buyer is happy with it. Thanks you all for your help

 

[HansFranz]

Not to hijack the thread, but do coils commonly "kinda work sometimes weakly and intermittently"?

I have a Dolmar PS3410TH that has an "intermittent/weak" spark.
I changed the spark plug, no change.
I sprayed out the switch and contacts with electrical contact cleaner and compressed air ... no change there, either.
Can't seem to get it to fire for more than a fraction of a second, even with ether...and that's after pulling on the starter maybe 300 times.

 

[J D]

Not to hijack the thread, but do coils commonly "kinda work sometimes weakly and intermittently"?

With any coil it's possible to have poor internal connections or insulation breakdown that could cause a weak or intermittent spark. Generally now coils have electronics built into them, so there a considerably more internal connections & components that can develop issues over time.
I wouldn't say it's common for them to work intermittently, but a common mode of failure is that they stop working as they start to get warm... which is kind of the same thing, & electronically suggests an internal bad joint or failing component