Help needed: Shindaiwa M242 gas trimmer

[bertsmobile1]

I checked out the YouTube video. On that specific application the gas cap has a vent. On mine there is no vent. It is a solid cap. Having said this, I did not think that the tank actually held any pressure. In other words I was under the impression that the carb diaphragm pulled fuel in. I'll reach out to Joe and see what he says. Thanks for sharing the link.

No the pump pressurises the tank and air pressure pushes the fuel into the tank.
A fine point but you can not "pull" a fluid you can only push it . Some thing you should have been taught in high school physics .
So the pump pushed into the fuel tank .
Are you sure that you connected the carb properly ?

Then why is there a fuel in the carburetor?

No where did ahdofu88 say he ha pulled the carb apart and found fuel in the carb
What he did say is removing the cap fixed the problem and that the problem takes a while to happen
So that points to a tank venting / fuel pump problem
HE has also replaced the carb however no mention of where he got the carb from so it could be a dud carb from Scamazon

 

[StarTech]

Then why is there a fuel in the carburetor?

I going have correct this since for the revision didn't earlier. Sorry I did get corrected sooner but a customer came in the shop and I got off track while I check his Echo Hedger.

It have said "Then why is there a fuel pump in the carburetor?" And I don't mean the primer either.

This is the fuel pump for Walbro WYK-353 carburetor.


There is actually a fuel pump in the these carburetors. It creates a vacuum which from negative pressure pulls the into the fuel section and as the metering diaphragm open the metering needle pushes the fuel into the metering chamber. Under negative pressure (negative atmosphere) the positive pressure (1 atmosphere of greater)does get the fuel moving. When you create enough vacuum fuel or any other liquid can flow uphill. So I have to disagree you can't pull a fluid per say if you are using a vacuum you can. But if you physically get touch it and pull then you can't; unless, you are using something that creates a vacuum.

These carburetors can even the tank return line disconnected still pump fuel into the carburetor. Just makes a mess when the excess fuel runs all over the place.

 

[bertsmobile1]

You can not pull on a fluid
It is a fundamental property of fluids
The pump pushes into the tank then air ( or tank ) pressure pushes fuel through the lines to the carb
High school physics

 

[StarTech]

Then can you explain why the Honda 4 stroke I just repaired ran without the fuel cap (otherwords the tank had no pressure other one atmosphere, impossible forto build pressure when it is open.)?

 

[bertsmobile1]

Because air pressure is pushing the fuel from the tank to the carb
Put the cap back on run the engine for 30 seconds hen pull the fuel line off
Fuel will squirt out under the pressure that the pump has built up inside the tank .
The pressureised fuel delivery dates back to early aircraft practice

 

[StarTech]

Oh well I just like see how happens if there is no return line. Oh you mean that the fuel pump back flows pressure to the on the same supply line.

BTW don't even have to run the engine for the fuel tank to build pressure as all you got to do to shake up the fuel. Can be done even a regular fuel can.

And that Honda brush cutter here was ran for 30 minutes without a fuel cap so I can't believe that the fuel had develop any pressure during that time. But I could be wrong.

And my hen might just pull the fuel line off thinking it is a worm.