Saw won't start sometimes when hot

[jackganssle]

Folks,

I have had an MS362 for a couple of years. It's a great saw but sometimes I'll turn it off and attempt to restart it a couple of minutes later, and no amount of pulling will get it to fire. Is this vapor lock? Is there some way to prevent this.

When this happens I have to let it sit for a couple of hours, and then it'll start fine. The spark plug doesn't seem to be very gassy, so I suspect it's not flooding.

Thanks!

[Al_Smith]

Well first off all make certain you blow the sawdust out of it periodically .Many saws develop a habit of over heating the ignition modual .They won't start for all the tea in China then until they cool off .

It helps sometimes with some saws if you give them about minute or three of a cool down period after they've been ran hard which helps start them on a restart .

[AdkStihl]

Try richening up the low speed jet a little and make sure your tank vent is clear

[Al_Smith]

I've got several that although they run exceptional well will flood on a hot start .Why I have no idea .Medium sized saws that although most frown on the practice will fire right off on a drop start with the throttle held open .

Now don't get me wrong because I don't recommend it unless you're an old hand around saws because it is dangerious if it isn't done right .You can start them on the ground with the  throttle cracked but it would help if a person had three hands .

[WDH]

Sounds like the ignition coil.

[John Mc]

... It helps sometimes with some saws if you give them about minute or three of a cool down period after they've been ran hard which helps start them on a restart .

In case that wasn't clear, I think what Al is getting at is to give them a minute or three of IDLING after running them hard to let them cool down a bit before shutting off, right Al?

Vapor lock is caused by the fuel heating up and "boiling" somewhere in the fuel system.  This causes a vapor bubble where the system is designed to be flowing and pumping liquid. It can sometimes be hard to clear this bubble. When a saw is being run hard, you are constantly pushing fresh fuel through the system, so it tends not to boil. If you shut the saw down right after cutting, things are still hot enough to boil the fuel that is sitting in the lines.

Letting the saw idle allows the engine to start to cool down, while still pushing some fuel through, to prevent it boiling. It can help, if vapor lock is the problem.

On my Jonsered 2152, replacing the Catalytic muffler with a non-cat one helped it run significantly cooler, eliminating some of the problems I had with hot starts. The saw also has a bit more power with the more free-flowing muffler.

[Al_Smith]

I think what might happen with a solid state coil is the fact they are direct bolted to the engine cylinder .It being made of aluminum is a rapid disperser of heat .However the dissipation of that heat is reliant on the air flow over and around it .

If you run it hard and rapidly shut it down the heat from that cylinder will affect the scr's and so forth within the coil circuitry to a point they fail to operate .No air flow .

I had an old PM 610 Mac that it took me a while to figure that problem out .In addition to that  unknown to me it had packed chips tightly under the cylinder which you can't really tell without removing the shrouding .I learned though .

Generally speaking solid state moduals are trouble free but some have their quirks .