I pulled the tank yesterday (I’m embarrassed to say that I’m getting pretty good at it) and started hunting the leak. I recall seeing fuel all along the medial (left) lower edge of the tank and that it was running down/forward along that edge from the rear to the front. That made me suspect that I would find a leak somewhere near the back.
I rigged up the ballon and bicycle pump as per chapter 37, but was unable to find any leak. I know that pressure was escaping, as the little ballon became slightly inflated, but then deflated in about 5-10 seconds. Despite that, I couldn’t even find where air was escaping. (I suspect the fuel cap. Despite plugging the vent hole by tapping it 4-40 and filling it with a locktite covered screw, I just don’t think that the fuel cap itself is air tight. Even with duct tape.)
Moving into a more aggressive mode, I capped the main outlet and proceeded to fill the tank to nearly full; Viola! Not one, but two leaks. They are no where near the magnitude required to have created the mess I found last weekend. I will have to chalk that up to an inadequately tightened main fuel line fitting and will double & triple check that stage when I get there again. During the meantime, I have two small leaks to deal with.
Fuel leak: lower left forward corner
Fuel leak: upper right forward corner
I’m firing off a “how do I fix this” question to VAF and will proceed with the advice of the collective.