Kind of at wits end here...

I had recently changed the fuel tank screen/filter and have about 5 gallons of fuel in the tank. Car starts right up and idles fine in the driveway.

As I drive up a long inclining hill, maybe a mile or 2, and an incline of about 30 degrees, to get additional diesel for the tank it begins to stall and then finally does.

When I open up the hood, the primary/clear filter is filled with clean fuel and the secondary filter housing is empty.

Any easy answer here, obviously there is a fuel delivery problem. Shouldn't 5 gallons be enough to get me over that incline/hill.

When I let the car idle in the driveway, no issues. It's idling as we speak, with no load on the car.

Any thoughts, thanks