Hello Gordon, In a word, no.
With the Skyport "Rain-Pruf header tank gauge vented by a small forward-facing hole, size unknown, and the wing tanks on original 415-C fuel systems being vented by forward-facing holes, the 100+ MPH slipstream would pressurize said tanks somewhat. I doubted that the Ercoupe header tank venting solely via the additional clearance around the float wire in a position 90º to the slipstream would be so pressurized. Pressure (or the lack thereof) in wing tanks must be equal if fuel flow is to be equal. In the header tank, it is only important that no vacuum develop as fuel is consumed if gravity flow to the engine is to continue. Other than that, pressure is unimportant. The engine-driven fuel pump has one-way check valves inside so nothing can force fuel back through it. It sucks fuel from the tee in the line between the two wing tanks so long as either is not empty. Its output is restricted by a 1/16" orifice in the outlet fitting and flows into the header tank in a quantity beyond that which the engine can burn. The excess returns by gravity to one or both wing tanks, depending on how a given coupe is plumbed. So long as the fuel source is vented in some manner and an increasing vacuum as fuel is drawn is not possible, the presence or absence of atmospheric pressure is unimportant. On your Forney wing tanks...replace your vented cap (or plug the vent well) and with properly sealing gaskets, your fuel flow from them should even out. Only your header tank should have a vented cap. Regards, WRB -- On Apr 19, 2009, at 22:07, Gordon Smith wrote: > > > W Bayne said: I was not aware that the original nose tank gauge vented > around the gauge wire. (Thanks John!) > Sure enough, the cap wire hole is drilled .128 in diameter (slightly > over 1/8") and the wire is .0938 > in diameter (3/32"). I doubt the tank would be pressurized measurably > by such venting. > > Are you saying that the nose tank is vented small enough that is is > some what 'pressurized. If so does there have to be back pressure on > the fuel system to make the fuel pump work? > > Also, following this forum, I checked my Forney fuel caps. One is > vented, one is not. I do not have the same amount of usage out of each > tank. One will always have quite abit more gas left in it, when the > other one is empty. >
