Got me baffled !!!!

[Dodge]

This has got me pulling my hair out !!

The story so far we have a spare ms181 as a last resort back up and a bit of snedding if Req saw ,the bloody thing is about 3 years old no more than 2hrs use if that, still on the original bar and chain that’s how much its done!!!!  

Same fuel as the other saws never old stuff , well its always been a a bit unpredictable on the starting front probably why its got so low hours on it anyway a couple of weeks ago I was cutting a few small logs down to size for splitting the saw had been running for Aprox 5 mins I stopped it and as per norm it wouldn’t start right I thought lets see what’s causing this normal tests Ahh no spark good  new plug  nothing ummm  slapped the spark tester on nothing Ahhh the old coil problem disconnected the stop leads on the coil Nothing  umm new coil then. Ordered a new Stihl £38 one, fitted and yaaa away we go  1 hour later the thing wont start normal tests and NO SPARK umm must be a dodgy coil I contacted the supplier and a new one sent out ( Top marks to LS Engineering by the way very nice people !! )  new one fitted ran for about a min then NO SPARK Arrrgggghh

if I adjust it /move the coil it will work momentarily SOMETIMES , just to add I am rotating the fly wheel anti clockwise with a drill plug out , if I stop and then try again invariably there will be no spark

Stop wires disconnected

Resistance checks  1.7meg  ohms  through the coil to earth

1 ohm resistance through earth bolts to coil

2  Ohm resistance through earth bolts to cylinder head

Well I’m sure it can’t be another dodgy coil,

 fly wheel (which is where I thought we were going with this) strongly magnetic  and coil gap is set to the correct setting feeler gauge set  10 tho Tried various settings no difference !!

So to summarise good earth, all connections abraded degreased and tight  stop wires disconnected during test process

New coil,   strong magnetic attraction on the fly wheel correct air gap

What else is there !!!!!!!

[bmp01]

Coil to flywheel alignment across the face of the flywheel (not the 10 thou gap) ? Have you got the plastic spacer between coil and engine?

Try another new plug too?

 

 

[Dodge]

Yes mate plastic spacer in place and new plug fitted at the first fail and I have tried it with another old but working plug with no result I tell you Its vodoo !!!!!!!

but thanks for the advice

mate

Rog

[Yournamehere]

How are you checking for a spark?

 

If plug-in with in-line tester:

I've had a plug tester on a running mower show no neon light-up.

 

If plug-out:

I carry a jubilee clip + wire + croc clip contraption to ensure good earth to the body of the plug when testing with the plug out the hole rather than assuming that resting it on the head will work.

[Stubby]

Sorry . Did not read the no spark bit .

Edited July 15, 2018 by Stubby
Wrong info !

[Yournamehere]

ching!

what are you using between HT lead and plug?

 

If one of those looks-like-a-spring-from-a-clothes-peg jobs wrap a mini cable tie round it to hold it secure or try and get something more plastic-moulded-cappy type jobby in there.

[lurkalot]

Not had any problems with coils, not on these saws, probably changed about three in total.  loads on their strimmers and combi's though.

 

Had a few 181's where the little e-clip jumps off the choke shaft, so it doesn't operate properly, and loads where the rear handle has had a knock and the linkage has all jumped out of its seating's.  Also a few where the top throttle shaft sticks leaving it wide open.

[Dodge]

I have been using a spark tester that has got a plastic body with a spring inside glows orange when a spark is present large croc clip on the body of the plug to a confirmed good earth and as a last resort the MK1 thumb and little finger to good earth only after a number of no glows on the spark tester :-)

[bmp01]

This spark tester goes in series with the plug then ? Does it work if the plug has a short inside it ? I've posted before. ... only ever seen a failed plug once and it was with one of these little plugs. See picture,  this is a plug with an internal short, you can see the lines where the arcing has occurred. Get a new plug (or 2) and careful how the wrench interacts with the plug. ....

[Yournamehere]

12 hours ago, Dodge said:

I have been using a spark tester that has got a plastic body with a spring inside glows orange when a spark is present large croc clip on the body of the plug to a confirmed good earth and as a last resort the MK1 thumb and little finger to good earth only after a number of no glows on the spark tester :-)

All covered; all good then.

But check out the end cap. Bin the dust cover and use a mini cable tie.

Much pull offing and onning can displace the tabs on those clothes-peg-spring connectors.