Re: Fleetwin fuel delivery

[Don]

Not sure if your carburetor has the sintered filter in the glass fuel bowl, but if so you might want to try running the engine with the filter removed.
Does the tank retain pressure after running the engine? In other words, does pressure escape from the fuel cap when you loosen it after running for awhile?
If so, it would seem as though the engine is pressurizing the tank, and the tank is holding pressure. I would check the fuel lines, filter, and perhaps the pickup filter in the tank.
If no pressure escapes after running and loosening the cap, then there could be a problem with the engine/intake manifold, check valves in the tank, or perhaps an external leak in the tank such as the gasket.
The simplest way to answer some questions is to try another known good pressure tank.
Converting this engine to a single line system with a fuel pump and tank is not all that simple, and costs some money…
I would diagnose the two line system completely first, perhaps the solution is a simple one…