Bert: Without actually looking at the plane, I'd guess there is a leak in the return plumbing that allows fuel to flow into the cockpit when the tank is full. Fue;l leaking out the top, vent or filler cap should end up on the [outside of] the windshield, not in the cockpit.
Why you cannot duplicate the leak on the ground is a mystery. With the electric pump, static on the ground should be the most rigorous case. John Cooper Skyport Services www.skyportservices.net
