I have a couple suggestions for this. First, loosen the nut and back it off a few turns, but don't completley remove it. This will keep the pulley from popping off all the way and from loosing the woodruff key.
Now, the task of getting the sprocket loose you have a couple options that don't require pullers. One, I'd say is preferred, but I don't know if you have this required tool for it or not... basically what you need for first option is a long and tapering steel drift/punch type thing (I have one that's about 10"-1 foot long) it need to taper so that you can fit it alongside the injection pump, and stick the end into the hole that is in the injection pump mounting bracket that is closest to the pulley. The hole in this bracket to put the punch/drift through is right next to and a little bit below I think, the fuel inlet banjo. There is a hole there, if you look carefully you will see it. The punch need to be slender enough to make it through that hole, and then it will contact the pulley fairly close to the axis of rotation. And it needs to be long enough so that you can whack the other end of it with a hammer, clear of the other end of the injection pump. Give it a good whack or 2 (I like to use a heavy hammer like a little sledge, moving slower rather than a lightweight hammer that needs to be moved fast, as the lighter hammer seems more apt to get out of control) With good contact with a hammer through the drift/punch, the pulley will pop right off.
Option number 2 is if you don't have ANY tools - no puller, no hammer, no drift. All you need is a couple medium-long'ish M8 bolts. What you can do is remove the top 2 injection pump mounting bolts; the ones that you loosen to rotate the pump and adjust it's timing. back them all the way out and remove them. Then get some longer M8 bolts and thread them into the holes. They will stick through the female threads on the other side of the bracket, and will start to screw into the pulley. As they start to screw into the pulley it will push the pulley sideways some because of the torquing action as the bolts are not near the axis of rotation. So as the bolts make contact with pulley, bring both bolts up to torque evenly so that they press the pulley equally on both of the contact points without torquing the pulley sideways very much. Eventually the pulley won't be able to take that stress and you will find *dink* the pulley breaks loose. The thing I don't like about this method is that the bolts screwed into the pulley this way will chew up the pulley where they make contact a little bit. If you care about keeping everything in perfect shape including the finish of your pulley, this is not really desirable, however it should not really effect the function of the pulley and the marks will be on the inside where you probably won't be able to see them when the pulley is installed on the engine.
Hope that helps... there may be other ways to do it too, those are just the 2 ways I've been able to get those pulleys off without a puller!
Good luck,