1994 Ford F150 4x4 SuperCab

I'm losing sleep over this one. A few times since i brought this car a year ago. I try to switch over from one tank to the other and it stalls. At times I can't start the car in the front tank, but I can in the Rear ??

I thought it could be a bad switch, but what else am I missing...

Any help would be great !!

Could be the hoses or the fuel pumps between the tanks aswell.

That's all i've got, sorry.

it could be your cross flow valve