Once I have seen yet another cause of vapor lock - the gas cap!
This 3-wheeler we used to have would stop running occasionally. The solution
was usually to unscrew the gas cap (phsssst!) and you'd be on your way for
another 20 minutes or so. I think there's a pressure release valve which
should let air in which got plugged.
No air could get in the tank, so no gas could leave the tank - however, the
fuel lines and filter were full!
Of course this was a gravity feed setup, but I imagine if the fuel pump is
weak the same could occur. The problem is worse with a full tank of gas.
Hope that helps!
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