my dads jeep had a bad headlight switch so he changed it then when you cranked it it would start for about half a second then die crank it again and it does the same thing?!?!?!?!?!?!?!?
Is this fuel injected or carb? If it is F/I is it equiped with a Idle air control valve? not to familar with Jeeps, as far as a Ford is concerned this 9 times out of 10 is the calprit. hard to see that it would be related to the head lamp swich though.