1999 jeep grand cherokee sometimes it won't start

if it has electric fuel pump turn the key on but dont start the engine you should hhear the pump turn on. do a pressure test on your fuel pump

Get a hammer and punch. Tap on punch next to key while turning key. This will free up frozen tumblers in ignition

Maybe the ignition key is worn out and the ECM is having trouble, get a new key from the dealer ship.

No key can be in the off position, if not working check fuses.

you probably have a bad door or rear gate switch

IS YOUR STEERING WHEEL LOCKED? TRY WIGGLING IT WHILE TURNING THE KEY.

Review the started system, is in spanish but maybe this document can be help you:
- WJ-2002-Cherokee-Service-Manual-PDF-08BA-Sistema-de-Arranque
- WJ-2002-Cherokee-Service-Manual-PDF-08B-Sistema-de-Arranque

I hope that this help is OK.

Do you have an alarm on this? If you do, that is most likely the problem. There seems to be a problem with the alarms. You may want to have a new key made just in case. Sometimes the keys are magnetically charged and after time, it wears off.

try disconecting the battery leave for 5minutes then reconnect lock and unlock the doors should then start if this dosn't work disconect battery again turn ignition on [normal running position ] then re connect battery after 5mins one of these options normally work Steve

I work at jeep and this is very common. you need a new ignition lock cylinder. easy repair but you need to buy it from a dealer and bring the key and lock cylinder to a locksmith to get it coded