you'll have to bleed the system. Don't just crank it untill it starts, you'll end up out of fuel & need a starter. If you had a little air tank it would help to pressurize the fuel tank a bit. Follow the feed line from the tank, it should go to a lift pump on the engine, then to the filter. Sometimes there is a hand pump on the lift pump so you can prime most of it by hand. I don't think there is on yours. So, crack the bleed screw on top of the filter, if you can't find it loosen the outlet line going to the injection pump, and try to get fuel out of there. When you do, tighten it & go to the injection pump. there should be a lower bleed screw & an upper. 5/16" wrench size, bleed the lower one first, then the upper. The upper will have to be bled be cranking the tractor. When fuel comes out there, crack the injector lines & crank till a steady squirt comes out, tighten & you should be all set.
Don't crank the starter for more than 25-30 seconds at a time & let it cool for a while between cranks. Make sure your battery has plenty of power.
Then scold the Father-in-law for running out of fuel, this is a totally unacceptable event that should never happen to anyone on any piece of equipment.
