I have a 90 XJ 4.0
Problem being... recently it has not been able to start in colder weather (around 30*) it will run for a second or so then die, but runs great on warm days. I checked spark, fuel ect... then noticed that if ign was held in start pos (without letting it spring back into run pos) the Jeep will run normaly...WHAT?!?! :disappoin At this point i am very confused and am seeking help. Also i recently replaced the crank pos sensor.
Any ideas or help will be greatly appreciated.
Thanks.

Check your Ign switch at the base of the column.

Well, i found the time to replace the switch (have a parts jeep)... only problem now is that its 65* outside! but i live in MO so the weather changes like that, and like our MO weather its supposed to turn off cold again and snow tonight and tomorrow so i will post my results when the snow starts flying!