Primer bulb drawing air

[adw]

Stubby is quite correct, i thought you had already changed the PURGE bulb? if the the non return valve in it is not working then the fuel will just go back and forth.

[Phil H]

The air is drawing from the carb when the bulb is released but no fuel/bubbles flow back towards the carb (only flow towards the tank) when the primer bulb is pressed so it to be working correctly

[Ratman]

Have you cleaned carb and fit new kit/needle/diaphragms etc?

[Phil H]

Yes, after the dirty fuel episode & been temperamental since.
Actually, I ran it for 15 mins or so yesterday and all ok but drawing lots of air today for some reason!

[RobMort]

....an old thread but still relevant.

I have the same problem but I think the problem is the the main-jet check valve not closing  allowing air back into the fuel circuit when applying suction from the purge bulb.

[woody paul]

Are you saying no fuel in bubble when pushed. 

[RobMort]

Yes, or very little fuel in bulb.

 

The way to see if the main-jet check valve is working is (https://arbtalk.co.uk/forums/topic/133943-walbro-carb-problem/page/3/#comments

 

H screw out, pipe over H jet opening, thumb over the fuel feed to the main jet, now blow/suck, you should feel the check valve open and close, no close and it’s not working.

 

Edited April 26, 2024 by RobMort

[woody paul]

Tank breather, try with cap off, 

[HillyJohn]

Another way to check fuel supply and main jet check valve is to use a medical type syringe. First try and fill from the carburretor intake hose, if hard to draw then check tank air inlet and fuel pipe, should be no bubbles, unless there is a split in pipe. Then draw from pipe connecting carb to primer, if check valve faulty lots of small bubbles in fuel. After use pull syringe apart, spray silicone on rubber seal, store in 2 parts or it will stick fast!