Unfortunately, the quality of "rebuilt" fuel pumps these days ranges from "Bad" to "Terrible", to "Totally useless". "New" ones aren't much better. As much as I hate to say so, you might need to gut out one of those pump housings and convert it to a dummy with a hidden electric pump actually supplying the fuel. Loop a piece of tubing through the pump housing and remove the lever arm and other hardware, then use a blank gasket between the fake pump and the crankcase. Hide the electric pump back under the cab somewhere and use an oil pressure controlled relay to shut the pump down in case the engine stalls.
Jerry
