whywont

Hey guys I'm running out of solution for my Jeep. I have a 95 Xj with the 4.0 I have no spark. Things that have been replaced (plugs wires cap rotor distributor pick up coil cps ignition coil) still no spark. using a volt meter I have power coming out of the ignition coil to the cap but when I put a spark plug in the boot for the ignition coil I get a really weak spark almost nothing. I put my volt meter in the boot for the ignition coil and it shows when I'm cranking the motor I am losing power. We then tested my buddies 93 xj and when he cranks the readingsome are off the charts. Also we checked the plug that goes into the coil where his showed that only one side had power, mine showed it had power in both. Any advice at all is welcome. If I need to re explain so thing I can. Thanks.