Gas Tank Antiflow Back Valve

[13crazyhorse]

I pulled the fuel line off my boat between the water separater and the tank. There's an little fitting just before the tank with a steel ball in it. I'm sure this is supposed to keep the fuel from flowing back into the tank thus aiding in faster starts. My question is when I try to suck through this gadget it seems really hard to draw anything and it makes a kind of vibrating sound. Seems like it should be easy to draw air through it. I hooked my hand pump siphon up to the hose before I removed it and it could barely draw gas through the line. Maybe it's gummed up or wore out? Any comments would be appreciated. Thanks.

 

[Home Cookin']

Re: Gas Tank Antiflow Back Valve

that's the anti-syphon valve. mine vibrates when I squeeze the ball. I was having fuel flow problems and suspected that part and replaced it. If your boat is misbehaving, that may be the problem. They aren't expensive to replace. You canalso test it by temporarily relpacing it with a same size fitting without a valve.

 

[Fireman431]

Re: Gas Tank Antiflow Back Valve

They also work much better under pressure then they do under a vacuum....meaning they open easier and stay open when fuel is pushing against the ball than when trying to draw fuel around them via suction.

 

[Don S]

Re: Gas Tank Antiflow Back Valve

I pulled the fuel line off my boat between the water separater and the tank. There's an little fitting just before the tank with a steel ball in it. I'm sure this is supposed to keep the fuel from flowing back into the tank thus aiding in faster starts.

It's called an Anti Siphon Valve, and it's only purpose is to prevent gas from siphoning out of the tank and into the bilge should the fuel line going from the tank to the motor get cut, broken, or disconnected.
Has nothing to do with the engine or keeping the fuel in the line.
It's installed in the pickup tube fitting in the top of the fuel tank before the hose going to the motor, and not on the pressure side of the fuel pump.