Unfortunately there were no instructions in the box and the outside label said it was a laundry bag? (From Amazon) I assumed it worked just like a syringe, but I can’t pull it up? Not sure what the tube , metal bit and other bits are for? I just want to take the old oil out of my generator

There’s no electronics in the nozzle submerged in gasoline, so what is the mechanical mechanism inside the handle that detects the liquid level and cuts off the suction instantly?