Did you get your turtle to teleport? Also, why not have the refuelling done locally instead of teleporting?
function refuel() -- Calculates what the minimum amount of fuel it needs to run its cycle and gets a bit more for good measure
local fuelNeed = math.ceil(((rows*rowLength) + 4*(rows-1) + 80)/80) -- [[This calculates how much fuel the cycle of my cactus farm will consume. You can safely ignore it or come up with your own formula]]
if turtle.getFuelLevel() <= 250 then -- [[250 is defined like that as a relic from when I was testing, it should be fuelneed*80 but, again you can ignore that]]
turtle.select(slot) --[[The missing part of this function was about selecting a vacant slot called slot. Change it to any number]]
turtle.suckUp()
turtle.refuel(fuelNeed) --[[ fuelneed represents about 3 charcoal in my program, I think yours is roughly in the same area so you could type turtle.refuel(3) or any number really (limited by stacksize)]]
turtle.dropUp() --gets rid of the fuel it didn't need
end
end
Are there any bugs left in your program?
What are the pistons for anyway?
Also, I haven't told you this before (or maybe I have and don't remember) but you can disable the requirement for turtles to need fuel in the computercraft config if you are still having issues with the refuelling stuff.