Truck stalling out after switching to primary tank

[71threequarterton]

This seems to be happening every time I switch from the auxiliary tank back to the primary tank. I've had the truck for maybe a couple months or so. It was a long trip to drive it home when I bought it so I filled up one of the auxiliary tanks and ran off that for a while once I made it back home. When I switched back to the primary tank the truck stalled and I had a hard time getting it started back up again. That was probably about a month ago. Once I got it back up and running, I've been driving ever since with no problem, running off the primary tank. I made another long trip a couple weekends ago and ran off the auxiliary tank again until today when I filled up the primary tank again. So I switched back over to the primary tank and it's stalling out on me again. Any idea what's going on here? I'm currently having trouble starting it and running off the primary tank.