If you have a 4.2 your fuel pump is mechanical, I do not know what you mean by cutting power to the distributor, I guess you have tapped on the line that provides power to the coil, the distributor itself has no power, or maybe you interrupted the connection between the distributor and the ignition module.
You need to install this part
Radio Shack part number 276-1103.
There is a brown wire coming off the alternator, this is the battery charge wire, you need to install the diode to prevent the current from flowing back from the battery to the alternator, diodes have a "side" to them so make sure you install it the right way, you can test this with a multimeter and I know there are marks on each side but can't remember now what they look like, just use the leads of the multimeter to check for continuity, one on each side, when you get a good reading you know you have identified the flow direction.
I did this on my YJ when I installed my MSD ignition box, I do not know why a stock YJ would have this problem, the MSD runs on so little current that a few volts coming back from the battery to the alternator were enough to keep it running.
Use proper soldering when attaching the diode and when you are done cover everything in shrink wrap.
If you need help I can take a picture of the wire but later today when I get off work
Originally Posted by JeepHammer
I don't mind writing for Fernando because he reads, and re-reads EVERY WORD!... Good to write for someone that actually READS the answer, and takes time to UNDERSTAND what comes back for an answer!