039 got me scratching my head?

[Detroit Dazzler]

So not sure what's the malfunction but starts stalls when giving it gas, will idle on its own, if you tip the saw on its side loosen the fuel cap it will come to life with no problems, tighten it up and it will run for a bit then return to the same thing. Seems like its pressurizing the tank but how? I've replaced fuel line, carb, and new fuel tank vent hose with the little screw in the hose

 

[ironman_gq]

Sounds like the vent isn't letting air into the tank and it's pulling a vacuum.

 

[boltonranger]

Perhaps a weak or torn carb diaphragm?
By flipping it on its side you may be aiding fuel flow by gravity. It certainly is starving for gas when in upright position.
Other fellas may have more insight.
Just a thought.

 

[Ozhoo]

I would be very suspect of that fuel hose.... especially if you used a screwdriver to persuade it into the tank.

 

[HarleyT]

Or if the new hose is an aftermarket/crap one!!!

 

[Detroit Dazzler]

Went to the Stihl dealer and picked a new vent hose, going to install it tomorrow and see what happens, I'm wondering if I put the screw in and it sealed it tight in the hose

 

[HarleyT]

I meant fuel hose....

 

[Honda_man]

Went to the Stihl dealer and picked a new vent hose, going to install it tomorrow and see what happens, I'm wondering if I put the screw in and it sealed it tight in the hose

Of all the components mentioned, it's the most likely. If it appears to be drawing a vacuum in the tank you need to locate what is preventing the vent. The vent hose seems most likely. Frankly, that style vent hose seems a little archaic for 2017, in my opinion. Surprised they haven't come up with something more "high tech." Lol

 

[HarleyT]

Just remove the vent line and try the saw. It may splash a drop or two, but see if the problem goes away.

 

[Honda_man]

Just remove the vent line and try the saw. It may splash a drop or two, but see if the problem goes away.

True. Or at least remove the screw from the vent hose.

 

[pioneerguy600]

This particular problem often occurs if the grub screw it turned into the hose, it cuts a thread and seals itself as it goes, the grub screw must be slid in and not turned in ,to allow air to make its way around the threads after install.