im shooting in the dark here, but fuel injected vehicles have a safety shut off to cut off fuel in the event of an accident, if that safety switch was malfunctioning, it could be cutting off the fuel supply when you hit a bump. i dont know if or where it is on a yj.
other things id check would be for a short in the fuel pump or possibly a short on an ignition component thats grounding. how do you get it restarted after it dies?
'90 YJ, ford 8.8, SOA, lincoln front, aussie rear, 4.88s, swampers.