1990 yj. Did a 4.2 nutter bypass, 2100 carb, new distributor cap, pickup. fires sometimes. I have driven it. Most no fire. I put a different ECM and it seems more sensitive to some issue with it sparking. When it runs it runs great. i cant see a crank position sensor anywhere. I bought Jeep with this problem. i have 12 volts to the coil and going to the distributor thru the coil wire to yop of distributor. I cant figure it out. It will start after the battery is unhooked sometimes and runs for a a bit this shuts off. Any advice?