Quote:
Originally Posted by Jersey Joe
Nobozo
I did not know about the Anti-Siphon valve either, until a mechanic told me to check it.
Apparently, what it does is prevents the tank from emptying inside your hull if you should develop a leak (at least what he told me). It is a 1 - way valve from the tank to the vent. If fuel runs out of the tank too fast, the valve will close and create a vacum in the tank. Mine was all crudded up with an off white crusty buildup, probably from ethanol.
The Mechanic I was working with told me that this would make sense for my problem - because the boat will run fine at idle, but when you push the throttle down, once you burn off the fuel in the carb, you can't pump enough fuel back into the carb to keep it running above an idle becuase the valve creates a vacum lock in the tank. In my instance, if you let the boat sit for a half hour - it will run fine again - which would make sense as air gets back into the tank to break the vacum.
I am no expert - just adding what limited knowledge I have to help a fellow boater.
Hey BigDog - I carry a wrench that fits my drainplug on the boat at all times, much easier and quieter than the C-4  |
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Thanks Joe for your response. It got me to thinking and got me off my butt to do some Googling and here is what I found that makes sense to me:
Question: My fuel tank is higher than my engine. Do I need an anti-siphon valve? There is a small round valve installed just above the tank where the fuel line leaves the tank. Could this be some sort of anti-siphon valve?
Answer: The valve to which you are referring is probably a small spring-loaded one-way check valve. The spring-loading on the valve is sufficient to prevent fuel from passing through it statically through a siphon (usually no more than 2 or 3 psi), but low enough so that the fuel pump can pull fuel through its mechanism while the engine is running.
These check valves will sometimes create a problem with electric pumps, since they (electric pumps) are less forgiving of even slight increases in suction head than are mechanical pumps.
If there is a wire connected to the valve on your boat, it is probably an electric solenoid valve that spring-loads closed whenever the ignition switch is turned off, and power is removed from the valve. These valves have the advantage of adding virtually no head loss to the suction side of the fuel pump, but they are vulnerable to malfunction, since they rely on electrical energy to hold them open.
It is not at all clear to us that either of these valves is actually required by the Coast Guard. In our experience, most people rely on a manual valve to prevent fuel from passing from their fuel tanks when the boat is left unattended. - Updated: January 5, 2004
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My take (NB): In Short; This valve is a TWO STAGE valve allowing gas to be
Sucked through it by the fuel pump, but will NOT allow fuel to "Siphon" out "on it's own".
Thanks again Joe for a teachable moment. I learn something new every day.