2G Walbro fuel pump cutting out / engine bucking or missfire.

[Brad Bell]

I've been having this problem for a few weeks but it seems to only happen under extreme load, or starting from a complete stop in some instances. it's a walbro GSS 342, 255LPH. Engine primes and starts fine, but after running for 15 minutes the I can hear the pump sputtering. Walbros as we know have a distinct whining sound, which mine makes fine when cold starting. The engine however will randomly start lossing power and misfiring when under load. Such as trying to go up a hill in 5th gear and you step on gas. It also happnes periodically when starting from a complete stop, the engine will start spitting rapidly and buck hard. My A/F gauge totally goes lean at this moment too. Is my pump dying on me? My sparkplugs bad? I have a rising rate fuel pressure gauge also, and it will not raise the fuel pressure past 60psi, which I need to run my 8psi efficiently.
Please help!

 

[Armando Elepan]

Awesome.