Fuel Tank Check Valve / Anti-Siphon Valve

[metriccrescentwrench]

I'm restoring a '79 Checkmate and noticed that there's a check valve in the hose barb on the fuel pick-up. I did some searching of these forums and noticed a couple of people point out that this is an anti-siphon valve. SO, since my fuel line is going to run uphill a couple of inches to a fuel filter/separator and then uphill to the outboard engine (with the fuel line secured by Adel clamps up to the point where it enters the splashwell) what's the point of that valve being there? I appreciate the safety aspect of not allowing fuel to siphon out of the tank in the case of a damaged fuel line, but I can't imagine that being possible in my case.

Thoughts?

 

[TilliamWe]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

You're thinking exactly backwards.

It's to keep the fuel from running out of your carburetors (or fuel system in general) and back INTO the tank. If it wasn't there, you would have one heck of a time "re-priming" the entire fuel sytem, everytime you went to start the boat. You will definately need yours.

 

[seabob4]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

This might explain some things...
http://edocket.access.gpo.gov/cfr_2008/julqtr/33cfr183.568.htm

 

[metriccrescentwrench]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

You're thinking exactly backwards.

It's to keep the fuel from running out of your carburetors (or fuel system in general) and back INTO the tank. If it wasn't there, you would have one heck of a time "re-priming" the entire fuel sytem, everytime you went to start the boat. You will definately need yours.

Yes, but there's a check valve in the primer bulb, right? Wouldn't that serve the same purpose?

This might explain some things...
http://edocket.access.gpo.gov/cfr_20...cfr183.568.htm

Thanks for that link. So indeed it is an anti-siphon valve. It appears that in my case it's not needed because my fuel line will be above the tank all the way to the engine.

 

[Silvertip]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

leave the anti-siphon valve in place. Just because the route to the engine is uphill does not mean the valve is not needed. If the hose between it and the next fitting in line should develop a leak or that hose breaks off and drops down, that route is no longer uphill but downhill. The ONLY time that valve would not be needed if the longest length of hose or line can NEVER fall below the level of fuel in the tank. Fuel cannot siphon in that scenario -- and for the record, there aren't many of those scenarios.

 

[gss036]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

The valve definitely prevents siphoning. On my old tank, I did not have an anti-siphoning valve and could plug in a female (engine end) fuel connector and pump the primer a few times and get the fuel flowing and it would run all day unless I raised the end or unplugged it. My new tank has an anti-siphon valve and it will pump fuel with the primer but I cannot get it to flow enough to siphon on its own, have to keep pumping the bulb, so it definitely serves its purpose. I like to pull gas out of the tank for lawn mower etc, and now it is a pain. This seems a little bit opposite of what some are saying but it does cause enough resistance with the spring loaded check ball to not allow fuel flow.

 

[Bondo]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

It appears that in my case it's not needed because my fuel line will be above the tank all the way to the engine.

Ayuh,... That's Faulty reasoning...
What's Uphill while on the trailer, Ain't necessarily uphill when in the water...

It's been working Properly for the last 31 Years,....
What makes you think it's gotta Go,..??

 

[Randy J]

Re: Fuel Tank Check Valve / Anit-Siphon Valve

Re: Fuel Tank Check Valve / Anit-Siphon Valve

bought new today at local OMC dealer no check ball just brass barb said didnt need it for my i/o v-6 well original aluminum was broke when i R&R fuel hose today so i duno???