Engine doesnt turn over to start when i turn the key. seems to have power just no crank

When you turn the key on you should beable to hear the fuel pump come on. Other than that you have a fuel pressure test port, looks just like a tire valve stem get a little probe press the valve after cranking fuel should come out strongly and not dribble out. If is doesnt seem to be firing your going to have check the coil pack for spark from the coil pack take one plug wire out and put it in a position that as you crank the vehicle you will be able to see spark jump or even hear give it a 1/4 air gap from its connection. If you dont have spark and your timing chain isnt broken you need to check for power the choice of tool is a test light.or volt meter. If you dont have either test tool we will go by sound when you turn the key on the engine fuse box has relays do you hear them click. That click noise will be fuel pump relay and PCM relay for power inpect those relays for corrode connections you mainly have a power problem and inspect for proper ground a missing ground can also cause the ECM to not fire the coils

Do you have the year make and model.? If it is a anti theift with a key immobilizer the vehicle will just start and idle for a few seconds then shut off and the anti theft light will remain on or be blinking. Then we know you are dealing with the anti theft. do you have another key to crank the engine if you do use a spare key and hold the key next to the immobilizer and crank the engine see if that will give if it doesnt try this method. roll the window down with window down disconnect the negative battery cable wait 5 minutes reconnect put the key in the ignition but dont crank it just yet turn it in the on spot not the crank for 2 minutes then crank it and see if that start the vehicle . If this doesnt work then you will need to call a mobile locksmith who reprograms the immobilizer

does it click? What happens when you turn the key?

the starter cranks the engine, the switch in the trunk has a button that you depress to reset the fuel pump. if the fuel pump doesnt operate then the switch may tripped, the button is DOWN. So does the engine crank? does it not crank? cranks but wont run? if it cranks but wont run, then check the switch in the trunk. Power goes to that switch and then to the pump, so if that switch has power going through it, and the pump doesnt work, the pump is bad. when turning the key on you should hear the pump go on for 2 seconds.

There are only two problems with electrical circuits. Too much amperage or too little amperage.We have to determine what you have.
An excellent test is to put your test meter red lead on the positive battery post and the black lead on the negative battery post. Crank the engine and record the voltage. Then place the red meter lead on the starter's battery terminal and the black lead on the negative battery post. Again crank the engine and record the voltage. The two voltages should be with in one half volt of each other. If the voltage difference is greater that one half volt, there is a resistance in the circuit, somewhere. I would expect the voltage to drop a volt or two, max
If the voltage dosent drop, there is high resistance resulting in low amperage. If the voltage drops too low then there is low resistance resulting in high amperage.
High resistance=dirty terminals
Low resistance = shorted wire, slow turning cranking motor maybe caused by bad starter, bad battery or hard to turn engine. ( engine bad, alternator or power steering pump bad, a/c pump bad, etc)
Can use head light for test. Turn on lights and note the brightness. Crank engine. If while cranking, the lights stay bright= high resistance.
If lights go dim = low resistance.

Alarms usually won't allow the engine to crank. If it is the alarm, arming then disarming it usually gets them to start. However, you probably aren't that lucky. Probably the most common problem for Cherokees with ignition issues is a crank sensor or a fuel pump. Listen to hear if the fuel pump runs when you turn the key to the run position (it will only run for 2 seconds, so have someone else turn the key while you listen at the gas filler neck)

Doesn't that jeep have an on board anti theft system that shuts of power to the startee and the fuel injectors. Im pretty sure it does thats where to start sometimes just turn the key to the on position for 30 sec. To 60 sec then crank the engine if that doesnt work turn off at least 10 sec try again tirn to on position without cranking motor for at least 30 sec then try cranking

More than likely, your starter has gone out. If the battery is fully charged and its not even turning over, that is what i would start with.

sounds like a bad ignition switch, its robbing power from the elctrical system when you are cranking the engine but as soon as you let off it restores power again. sometimes just in time to fire while the engine is still cranking. hope i could help

sounds like you need a new battery, it probably isnt running enought cranking amps to start your car, try a different battery and it should start fine