Stihl 066

[Mesterh]

Disconnect the on/off switch wire from the coil and see if it sparks then. If not then there's your problem.

[woodbodger]

Yep the earth wire is connected I guess the other wire is for the off switch?

[swinny]

Yep the earth wire is connected I guess the other wire is for the off switch?

 

yes, sorry i meant the on off wire isn't contacting when it shouldn't be

[woodbodger]

Right just to confuse matters I have tried again; moved the coil as tight to the flywheel as poss and now I just get a blue spark but only by pulling the starter cord at a speed I couldn't hope too match with the plug in even with the decompression. I would prefer to see no spark then I would KNOW that the coil was at fault.

[Mesterh]

The air gap between the coil and flywheel should be something like 0.2mm. It does sound as though its knackered. You would get a nice spark with not much effort.

[swinny]

Right just to confuse matters I have tried again; moved the coil as tight to the flywheel as poss and now I just get a blue spark but only by pulling the starter cord at a speed I couldn't hope too match with the plug in even with the decompression. I would prefer to see no spark then I would KNOW that the coil was at fault.

 

there needs to be a small gap between the coil and flywheel

 

all your contact points need to be as clean as possible, the flywheel area needs to be nice and clean, the pick ups on the coil also, check ht lead secure in the coil, check good fit from ht lead to the plug top

[swinny]

The air gap between the coil and flywheel should be something like 0.2mm. It does sound as though its knackered. You would get a nice spark with not much effort.

 

as above lol we seem to post at the same time

[rxe]

The air gap between the coil and flywheel should be something like 0.2mm.

 

Stick a sheet of paper between the coil and the flywheel. Turn so the magnets are pulling the coil close, loosen the coil bolts, then re-tighten. Remove paper. This is close enough to the right setting.

 

And - the coil is made up of a laminated core. Are these rusty and starting to split apart? If the metal part of the coil is corroded, it will weaken the spark.

Edited September 7, 2010 by rxe

[tommer9]

I had a lot of problems diagnosing a problem on a strimmer. It turn out coils can be intermitently faulty. This was on an echo strimmer. I've had it happen on 3 or 4 of them so obviously a fault that occurs with them over time. Must admit I haven't had it happen on anything else, (other than a mini - but i don't think that counts...)

 

R

 

I have never heard that a coil can be faulty. I think that your intermittent fault could have been coil related, such as one of the points where a wire connects to or exits from the coil being worn etc, but they just do not have intermittent faults as such. I have had this out a couple of times with different service engineers (2 of which have about 80 yrs experience between them).

[TimberCutterDartmoor]

Yes old fashioned coils used to be revivable by baking in the oven but this is a modern electronic coil we're talking about with contactless discharge not back EMF. The irritation with them and their assoc. components can be flippin maddening since really the system has few inherently troublesome parts. GardenHireSpares on ebay regularly has parts like this and is well worth emailing or phoning.

 

Here is a damn close example of what he stocks and would no doubt help you out in getting the exact part.

 

IGNITION COIL COMPATIBLE STIHL 044 046 048 MS440 MS460 on eBay (end time 23-Sep-10 15:49:47 BST)

 

When you crank it over with a supposedly working spark is there an unburnt or slightly burnt smell from the exhaust? Is the plug gapped properly (new included - always overlooked and yes your saw manual should quote a spark plug gap in the data / maintenance table) ?