Are you getting the "Check Engine" light? Have you run the trouble codes? There's a lot of things (sensors mostly on these jeeps) that it could be but my best guess is that it might be your CPS (Crank Position Sensor). Mine went south once and my Jeep would not stay on without me keeping my foot on the gas all the time... swapped it out and no more problems. But again, BEFORE you spend money on the sensor or anything else run your trouble codes... On Jeep ZJ's just cycle the ignition key On/Off/On/Off/On within 5 seconds (you don't turn on the jeep) then the codes will flash where your odometer is located... it will start with "12" and end with "55"... any other numbers flashed inbetween will be your trouble codes. Hope this helps.

Fred R.