RE: OS 91 FS Pump not pulling fuel. Help?
If you remove the glow plug, disconnect the pump from the carburetor and then spin the engine with the starter, does fuel come out of the "out" port of the pump? If so, the pump's working fine, and something else is wrong. If your pump doesn't work, but did at one time, then it's gotten some kind of trash into it that's blocking an internal passage. Trash getting into pumps is common. You must be absolutely sure that you are filtering your fuel when it goes into the tank, and then filtering it before it goes into the pump. Do not use muffler pressure, that will put trash into the tank. Just vent the fuel tank from forward top and have it discharge out the bottom of the cowl/fuselage.