There is no special tool required, you just press the plastic ears against the metal line - the male line - and then pull the coupling apart.
When you pull it apart you will have a plastic piece and it should have two O rings and 1 spacer. The Jeep mainteance manual says you have to replace the plastic piece and the O rings every time you have the joint apart.
You need to go to your local jeep dealer and buy the "fuel line coupling repair kit". The parts guy will know what it is, expect to pay around $15 for one of them and if you pull of the fuel injector rail you will need two kits. The kit comes with the plastic piece, the O rings and the spacer. In addition, there is an installation tool which you place the O ring, spacer, O ring then plastic retainer on, then slide it into the female part of the coupling. When you hear the plastic ears "click" then you can pull out the installation tool.
When you prepare the joint for reassembly use a bent paper clip to pull out the old O rings if they did not come out with the fuel line. Make sure no O rings are left in the coupling before you install the new repair kit.
Do not try to reuse the coupling. You are dealing with fuel under pressure and being cheap could result in an engine bay fire and loss of your XJ.
