I agree, you don't want to starve the fluid out while doing this process, but as long as oil is pumping out, you have not starved it. This is the reason for having someone in the vehicle to cut it off as soon as you seen new fluid coming out or if fluid isn't flowing out,then cut off. Keep adding, then restart. I haven't seen any starve if you keep adding through a full funnel of oil, but it's possible.