Stihl MS 290 No Spark

etbrown4

I see no spark on the plug when I ground it against the carb, and pull the rope.

I've tried 2 plugs.

I have the choke in the 'full choke' position.

I have the chain brake 'on' or thrown forward.

Shouldn't you be able to see a spark when pulling the rope?

What is the next step?

Any tips are appreciated.

etbrown4

Some say that you can't ground a plug against the carb on this model Stihl.

If so, how to you test the plug while watching for a spark?

etbrown4

I have found that sure enough, I do have spark.

To see it, I have to take a piece of copper wire, wrap it around the base of the plug and let the other end contact the head. Bingo, plenty of spark, though it's yellow.:smile2:

Now, the plot thickens. With 'ether' shot into the cylinder or through the carb, I am getting zero firing in the cylinder.

I've worked on lots of different motors including thousands of hours flying and working on 2 cycle ultralight airplane motors.

For now, I'm stumped. How can you have fuel and spark and no fire?:frown:

Is this unique to a Stihl, because I can't recall seeing this before and that covers 50 years of twisting wrenches!

ScottyAFoster

Pull the muffler and make sure that the cylinder is not lean seized. Yellow spark is iffy.

KevinE

Yellow spark is indeed "iffy"

Get the coil checked. It should be a bright blue spark.

If it was seized, I reckon a guy with your experience would know it.

Tony Knight

Yep you should have a nice blue bolt for spark.

Has the saw sat for any length of time as if there is no spark arrester/screen in the muffler the bloody mud wasps here will build a nest effective sealing the exhaust port I've had it in the past on a low usage saw and more recently on a brush cutter.

Regards


Tony

etbrown4

Problem fixed.

Prior owner had wrong plug and the gap was at .040 too.

I don't see how it ever ran!

Thanks for all the tips.

you guys were right. The yellow spark was a dead giveaway.

Many thanks,