Early morning PX flight from Wewak to Port Moresby (F28 or F100), passengers all on board, refuelling completed. Captain exits coughpit and disembarks, returns to coughpit and repeats exit, return. Makes following announcement: the fuel tanker can't restart and won't move and I haven't got enough room to swing the aircraft around for take off. We can either wait for God knows how long for someone to move the tanker of, if your are willing, you could all disembark and push the aircraft back giving me enough room to swing around. And that's what happened!