I drove a 1978 GMC Buffalo to Mexico several years ago for a church group and it had been sitting for several years with a 1/2 tank of fuel. I checked it out, drove it to a mech to have it checked further and got fuel on the way back to park it. Loaded the kids and gear and headed out. Got fuel in Redding and added some fuel system cleaner and headed out the next morning. After stopping at Cottonwillow rest area,it started up fine,but as soon as we started to move, it stopped. We got it towed in to Bakersfield at 4 AM and got a mechanic from Valley out on a Sunday AM to fix it. It turns out that there was the type of algae that grows in diesel plugging the fuel line and both filters. He changed thefilters and blew out the fuel line from both ends and told me to hot fuel it for the next couple of tanks. Gave us a couple of extra filters and I hot fueled it there in Bakersfield and just before we went into Mexico and didn't have a bit of trouble.
He also told me that you always want to park it with a full tank of fuel to stay away from that problem.