Gas spews out of fuel line when removed from carb - Husqvarna 36

[pcguy2u]

And when I remove the gas cap it stops until I close the cap and the hose starts to fill though more slowly and eventually stops filling. Very strange. Sitting here at my computer thinking about this and it occurred to me that it could have something to do with the piston but that couldn't happen with the hose off the carb, or could it???

Another clue is that the saw runs WOT with no load, but dies under load. New Chinese carb installed at this same time.

Any ideas? TIA, Nick

 

[Andyshine77]

Yeah you have to empty the tank, and I suggest removing the fuel pickup, before you pull the line off the carb, as the tank will always have some pressure. It's normal and we've all done it.

Sounds like a massive air leak, I'm guessing where the carb seals to the boot or block. How was the saw running before you replaced the carb?

 

[pcguy2u]

The saw was given to me by a buddy because he only needed one very seldom and the dealer wanted $200 to fix it and couldn't be sure if that estimate would fix the issue. The saw was doing much the same thing before I got it.

The part that is very confusing is that after putting the saw on its side and opening the cap, the pressure began to build again when the cap was once again closed. Thought about heat, but it was 58 degrees out and I hadn't run the saw but for a few minutes. BTW, the tank was less than half full when this happened.

 

[pcguy2u]

One other thing; have been using chainsaws for many years and have never heard air escaping from the fuel tank cap when being opened??? Including my Husqvarna 460 and my Echo CS-330t. I only offer this because some folks come here and have no background at all...

 

[EchoRomeoCharlie]

Fuel evaporates and will pressurize a sealed vessel with vapor. A fuel tank with closed tank cap and attached to a carb is considered sealed. The vent on a fuel tank is a one way check valve to let air into the tank so it doesn't pull a vacuum when you're sucking fuel out of the tank while running the saw.

So yeah, anytime you're going to pull the fuel line off a carb, it's smart to empty the fuel from the tank first and leave the cap off or it will most likely spit fuel out of the fuel line.

I hear gas escaping from the fuel cap a lot, but my Stihls are quarter turn and lest all the gas out at once so it's easy to hear. The threaded caps let the gas out more slowly so you may not hear it.

Less gas in the tank = more air/vapor to pressurize. So that makes sense as well. Full tank will have less of this issue.

That's all normal.

 

[pcguy2u]

The part that is very confusing is that after putting the saw on its side and opening the cap, the pressure began to build again when the cap was once again closed. Thought about heat, but it was 58 degrees out and I hadn't run the saw but for a few minutes. BTW, the tank was less than half full when this happened.

Forgot to mention that the above occurred with the fuel line open at the carb...

 

[Chevboy0167]

This happens all the time on this these small series of Husky saws. The duckbill fuel tank vent valve allows air to be pulled in when fuel level drops but not vent fuel vapors out to atmosphere. EPA crap.

https://www.partstree.com/parts/husqvarna-530026119/

 

[huskihl]

Tank vent, fuel line, and filter are working properly. That’s what they should do when you remove the line from the carb

 

[a. palmer jr.]

You could drain the gas and then leave the cap off before you remove the fuel line..

 

[pcguy2u]

Looks like the answer is that the buildup of pressure in the tank is normal and should have no effect on the operation of the saw.

Subsequent carb adjustments seem to be what the issue was/is. Have not used the saw for much more than a warm up and quick test, but it seems to be ok. If anything changes on that score I will post up here.

Thanks for the help, Nick