My 02' 4.7 H.O. Threw five codes the other night. Po171, PO174, PO300, PO302, and PO304
It turned over for like 15 seconds and finally started. I assumed the upstream O2 sensors were bad (wife says the fuel mileage has begun to decline in the last months). Changed them with the MOPAR ones. The 300 codes are now gone. But the 171,174 remain, and now the jeep just won't start. Turns over but no spark
New fuel pump relay( today) and filter/regulator (last six months)

 

Those two codes are associated with vacuum leaks. Not sure that would cause your WJ not to turn over. Could be your cam or crank sensors. It won't crank without a signal from both of those sensors. Maybe even your PCM going out.

 

A bad cam or crank sensor won't prevent the engine from turning over, it won't start, but it will turn over (crank).