I have been fighting this 90 XJ for a while now. Been about 4 years and still don't have it right. At the moment I have been dealing with the injector o rings leaking. It started with the fuel pressure regulator and now I cant keep the o rings from leaking. I have pulled the rail 3 times in the last month and it never fails that the 5th cylinder continues to leak from what seems like the rail side but I'm not 100% positive on that. Is there a way to know if it is something else causing the leak or am I just installing the rail incorrectly? It will not fire either, have spark have replaced everything from the fuel pump through all the lines and back to the tank, have done everything from spark plugs back to the started coil. Not sure what is going on and any direction would greatly help if someone has experienced this issue

 

My guess would be the rail is messed up just enough that the o-ring isnt fully sealed. Slightly out of round somehow, or its got dirt in it. Rail itself could be slightly bowed at #5. Dont know.

 

If they are the original metal bodied injectors, they can rust through and start weeping out of the injector itself. A set of refurbished 4-hole Bosch 746's would be the cure for that problem. There are a couple folks on here that sell them, and some eBay sellers. I got a set of refurbished and flow-match from someone on these forums for $70 about 4 years ago (he's no longer selling them though).

Also beware that some of the spark plug wiring diagrams are wrong. It's also possible to have the distributor in the wrong position on 180 out.
You should visit http://cruiser54.com/?p=68 for a correct chart and indexing procedure. Tons of other great tips and info on his site you should work through, especially improving the grounds.

 

My rail had some rust flaking in a couple of the injector seats that was tearing O-rings. Cleaned/steel wooled 'em up and was pretty sure I had good seals. Then thought "Is this a place where pretty sure is good enough?"

Got a new Crown rail, buck and a quarter, no leaks, one less thing to worry about.