Cherokee no start

2000 cherokee 4.0
My dad bought it with a bad engine. picked up a engine from a reputible yard and put it in. He is no dummy when it comes to cars...just not to up to date with computer controlled as he should be. Well the damn thing wont start, so I inherit the problem. I dont know much about these jeeps so we end up here.

engine will crank fine, pops a little but will not start. If I were to guess I would say the timing is off.

I did a pretty good visual, no plugs off, checked every plug to make sure they were clicked. All fuses are good. Fuel pressure at rail is 50ish. MIL is off. Scanned the computer, no codes. Checked the data stream. only thing I noticed that struck me as odd was there was o deg ign advance while cranking. Which might be completely normal. I dont really get squat for info since the engine wont start.

about the only thing I can think of is a screwed up crank trigger?

I would try spraying some starter fluid in the throttle body just to eliminate a fuel problem. Also you can download this 2000 factory shop manual, keep us posted.

http://www.lunghd.com/Downloads_and_Links/Downloads.htm