Question on 2 fuel lines found on smaller blowers and weed wips

[waylonJ]

I am hoping to better understand the function of the line which is connected to the primer. I know it goes into the top / upper hole on the tank. My understanding is that this line functions to push air into the tank which then pushes gas through the bottom / lower gas line. Am I right so far? By pressing the primer bulb it "pressurizes" the tank forcing gas into the carb. Right?

1. What is the function of the filter looking thing (I know it's not a filter) which is inside the gas tank connected to the top / upper line? Is it a one-way valve to allow air to create pressure in the gas tank?

2. Does this upper line described above have to stay out of the gas? I see they are normally tucked up into a corner of the tank. Is it okay if it's in the actual gas?

3. Is there a way to test the primer circuit to make sure it's okay and functioning? I know the bulbs can crack over time.

4. Is there a supposed to be gas visable in both upper and lower lines leading from the gas tank to the carb?

5. Is there supposed to be gas or bubbles visable when the primer is pushed? Anything to look for on the lower gas line to be sure it's working properly? Bubbles or gas moving towards the carb?


Many thanks to this site - I have learned a lot for you guys!

 

[Hammermechanicman]

The bulb on most 2 stroke equipment is not a primer but an air purge. It sucks fuel i to the carb to displace air to make the engine easier to start. The fuel supply line in the tank should have a filter on it. The return purge line to the tank just needs to be in the tank. The purge bulb has a check valve in it.

 

[bertsmobile1]

Close enough.
IT sucks the air out of the carb so that it is full to enable starting
Once running the fuel pump pushes fuel into the carb and what is not needed is returned to the tank .
It is easier for a pump to push than suck so the fuel tank has a vent in it which allows air to enter till the tank gets to a pressure of 5 to 10 psi.
This pressure pushes the fuel up to the pump .
To save on space and complexity the pump exits via the primer bulb on newer carbs
When pumping by hand it is near impossible to get all of the air out of the fuel line.
When not in use the fuel level in the carb will drain almost empty and the fuel line will also drain to the same level as the fuel tank so there is a lot of air in there.
In operation the bulb may or may not fill completely
f you see a lot of air in the return line with the engine running that indicates an air leak some where in the system.

 

[tom3]

That little plastic end on the bigger line keeps the line from coming out and I suppose meters the return gas from the carb for priming.

 

[waylonJ]

Okay - thanks guys!!