I have a GSL392 I believe is the part number. In this case it's feeding an 8.1 Vortec. I bought the vehicle in January drove it 400 miles in one day and parked it. It sat until sometime in March. I started it, it fired right away and idled fine for 2-3 minutes then gradually began to run poorly, I presume as fuel pressure dropped until it quit.

I took a look at fuel lines, replaced one. I can't get the pump to prime. Used a fuel transfer pump to push prime the Walbro the engine would run for a short time, firing with about 10 psi provided by the transfer pump. The Walbro was removed and inspected. Nothing unusual seen in either end. The pump runs and sounds fine. Put a six inch hose on the suction end and dropped it in a can of fuel. It would run but didn't pull any fuel. I have to assume something is wrong with the pump at this point. Is there a check valve in there that might be stuck? Is there some common failure mode whereby the pump runs but doesn't move any fuel whatsoever?

Has anyone experienced this with a Walbro or any other similar fuel pump?