Fuel Demand Valve

[mjl7245]

Q1: is use of a fuel demand valve necessary with an EPA-compliant portable fuel tank?

I’m planning to purchase a new portable EPA-compliant self-venting 12-gallon Moeller fuel tank for my Mercury 60-HP FourStroke EFI engine. The hoses recommended for the tank by West Marine do not include a fuel demand valve, which I have on my current 6-gallon tank.

—Matt

[jimh]

The function of a fuel demand valve is to prevent fuel flow from a fuel tank to the engine from pressure build up in the tank, and to only allow fuel to flow when the engine demands fuel, that is, when the engine creates a suction on the fuel hose. This type valve is typically used with modern EPA-compliant portable fuel tanks, as they typically will accumulate pressure in the tank because they are normally not vented to the atmosphere.

When you describe an EPA-compliant fuel tank as “self-venting”, I don’t know what you mean.

[mjl7245]

Thanks, Jim. That's a good question. I'm not entirely sure, either, but that is how the manufacturer describes it: " 2 stage self-venting cap that meets EPA and CARB Permeation Requirements". After a bit of online research, I think that means the cap is designed to vent automatically when the pressure gets to a certain PSI, thereby striking a balance between excessive pressure buildup and constant venting that the EPA has deemed harmful to the environment. But I could be wrong.

Matt