Jeep Keeps dyin', got a question

Ok, here's the deal. When going downhill, and not giving it throttle my jeep dies. I try to crank it back up and can't get it to turn over. Fuel pump comes on, get gas to engine, but won't turn over. It's done it about 4times at on different days wheeling and it almost always happens when downhill. It doesn't happen everytime, but when it does it's happened when downhill and low RPM's. Sooo, the first time it did it we popped the dist. cap and sprayed wd-40 because it was obvious the one before me hadn't changed it. After we sprayed wd-40 in there it cranked right up, got off the trail took it home, got a new cap and rotor replaced all plugs and wires. Now it's still doing it.
Today we went wheelin', pulled over to air down, wouldn't crank back up. Did wd-40, cranked up. then later i was wheelin' just got down climbing some rocks and started down a hill 1gear 4lo letting the engine to it's braking and it died on me. Couldn't get it to crank, let it sit for about 20-30 mins. watched the others wheel, came back to crank it I got nothing. Then i popped the cap off sprayed wd-40 in there it cranked right up. So far that's the jest of it. But now to throw in a mix, I was wheelin' in a creek, I was workin' my way over a large rock but couldn't make it so i kept bumpin it, and when I was backing my front off of it cause I couldn't get pulled up, my front bumper came down kinda hard on the rock and killed the engine. Tried to crank it samething, wouldn't turn over. We let it sit for bout 30mins while we tried to get the other guys in a position to tug me out of the creek we kept tryin' to crank it and same deal, won't turn over. But right before we hooked up I tried it one last time after about 30mins of it just sitting and it turned right over. I am completely stumped. So anyones help will be great. Sorry for the long book, but i'm just trying' to be explicit because I have no clue why this is doing' this and how to fix it.
Here's a recap:
-I6, 4.0
-Going downhill low RPM's jeep sometimes dies and won't restart, turn over
-Samething happened when I knocked the bumper hard on a rock
-Samething happened when I just pulled over to air down
-Engine is trying to turn over, just never does
-Fuel pump is running, gas to engine
-New Cap, rotor, plugs, and wires
-4-5times this has done it, everytime I spray wd-40/brake cleaner in the dis cap it cranks right up.
-Other than the creek run, all the other times were completly dry out, not moisture in the cap, and even in the creek there didn't apear to be any moisture in the dist. the engine was bone dry.

Please if you have had any experience w/ this let me know. I'm frustrated about whether it's electrical, ignition system, o2 sensor etc I have no idea.

I'm going to go out on a limb here and say that it might be the coil/coil wire connection that is giving you greif.
We had a cherokee in the shop I work at that had a similar problem, it would sometimes start, other times not, sometimes run perfect, other times run crapy, all because the coil wire at the coil was shoved in, but not making a good connection, so whenever it was bumped for some reason(removing the cap, hitting a big rock, ect...)it started or stoped working.
HTH

What Year Is It

it's a 96, keep the idea comin'....cause i'm completely stumped

Have you tried to intentionally make it die by wiggling wires and other parts .... :repair:

Bad ground, bad battery connections, vaccuum leak, loose distributor, would a bad crank sensor cause it ?

haven't tried to kill it by wigglin' the wires, i was just hopin the other times it did it were cause of the dist cap being old etc...but now it's still doing it....so i'm gonna have to start investigating more into troubleshooting it.
Does the dealership or somebody do electrical testing to see if there is a short, or bad ground etc?

Most dealerships will if they have someone knowlegable. But if it's electrical diagnosis don't expect it to be cheap. Dealers in MA get $80 an hour.