The other day one of my fuel injectors went out so I decided to buy a new one from automotivemachine.com. I put on the new injector and that soved the problem for a few minutes and then it started leaking again. I took it back out and this time it was the o-ring that was the problem. I replaced the o-ring on it twice and it is still leaking, but now another injector is leaking. So if anyone can tell me why this keeps happing and how to fix it, that would be awesome.

He may have givin you the wrong injector. 240's are notorious for leaky fuel injectors. Make sure you get the correct kind, or a better kind, and refer to a manual for installation. You can find a manual at your local library or on the net somewhere. Check out http://www.240sx.org Look at thier FAQ I almost positive has something for your problem. If worse comes to worse you could alway take it in. :squint

NOOOO dont take it in theyll rip you off big time. I had a leaky 3 leaky injectors on my 89 240 and I took it in and it ended up costing me 1200 dollars for the new 3 and installation!! I was stupid so I paid it and went on with my life

Make ABSOLUTELY sure you're using OEM o-rings, aftermarket rings seem to be mis-sized or cheap material, and before you put the injector into the rail spray it with a little WD40 to help it slide in easier. The o-rings can tear easily if you're not careful.