I put my key in the ignition, try to crank the engine, and everything goes dead. I let off the key and all power comes back on. Any clues, battery is fairly new.

automatic transmission or M/t manual stick shifted, not TOLD.
4.0L INLINE 6 BANGER, (a great engine for SURE)
owned me a 88 and 98 Cherokee and all books then and now .
old cars have many problem mostly ignored until more more problem sinks the ship.(holes in the hull)
first off PLEASE stop saying turns, use these words
the the starter motor "cranks" the engine or not
or starter motor cranks fast (robustly)_ but the engine "fails to start" and run and stay running.

the addED throttle TRICK (gasPEDAL) TRICK HINTS AT 2 things, IAC dead or engine is flooding but a Dead IAC valve kills dead all starting air, so does WANT TO flood.
engine needs air and fuel to start lacking air is only fuel FLOWS , see? (HARD FAIL THAT)
that is an engine problem and next is lost of electrical power. of some kind.

that under dash problem is bad wiring, and only tests with a voltmeter (15 CAUSES)
can solve bad wiring, I can't just magically do that here. in a text box.
see? but must happen. (called car repair shop)


https://imgur.com/a/NEpNtRr

BOTH THE STATER MOTOR TURNS (SPINS) AND ENGINE CRANKS SHAFT TO TURNS, BOTH TURN,
JUST Avoid the word turns, and win.
starter works or is dead,
starter does work and engine does crank bingo if can start and even run the engine. (sustained)


say starter cranks.
say starter is dead, or clicks ,or chatters or is silent or spins fast but engine fails to crank, at all. (yes starter motors have lots of fail modes)
then a good starter
the engine crank shaft then spins, called cranking, action
if it does the engine may START< RUN and stays running or even STALL out. even in 2 seconds after starting. JEEP ASD relay drops out? ASD can drop out for lots of reasons.(ask)

if the starter fails, dead, then shift to Neutral selected.
foot on brake pedal, key on, and shift from park to N
and crank the starter motor. (starting mode of key)
this is a trick to always learn and try. on cars A/T.

you keep asking others all blind what is wrong.
and get wrong answers too. so what do you expect from the blind?
all that is silly game.
are you going to replace 15 to 50 parts on a wild guess.?

learn to diagnose. the problem using 2 things
a voltmeter
and the service manual drawing (schematics) to find the voltage
lost and point of failure, and learn not to guess expect 15+ things possible even more. I have the service manuals here.


also tell what these words mean?
"the power will come back"
i've no clue. at all
when this POWER deal fails do all other things work in the car.
all lights say head lamps key off or on? both
IP cluster lamps dead.????? the do a self test each key on,
tell al thing dead with key switch ON? !

WHEN DEAD, A VOLTMETER (DMM) FINDS WHY IT IS DEAD
YOU PROBING THE 15+ POINTS OF FAILURE HERE.

https://imgur.com/a/NEpNtRr

LEARN TO READ THIS SIMPLE SCHEMATIC AND FIND
WHY THIS PATH DIES DEAD. 0V, CRANKED (START)
AND YES KEY SWITCH IS 1 OF 15 CAUSES. SEE ?

FIX STARTER DEAD FIRST, THEN WE REPLACE IAC.(or clean it_
on all my 4.0L every one ,owned 3 at one time.
the top failure was a stuck IAC , i unplug IAC and remove it and clean it fully. (degunked) this elect valve controls idle air and RPM all the time)even cranked !!!!!!!!!
it loves to stick from that black cloud of EGR+PCV actions.
every 50k miles or less. I then got wiser, and spray the valve cone tip
with this, mine was 3 way acting PTFE ,graphite. and more.



https://www.amazon.com/s?k=Anti-Stick+Lubricant+Spray&i=industrial&crid=3SZZXGVHFW1C4&sprefix=anti-stick+lubricant+spray+%2Cindustrial%2C97&ref=nb_sb_noss

this is not clear at all (is 3.4L engine my bet)
the starter is silent or not? if the starter motor spins the enigine crank shaft , fast that that is cranks ok not start engine.
no crank means. the crank shaft never spins
and that as a few causes,
blow fuse test them all?
crank in park and in Neutral too? N can work and P fail on any car.
no power to PCM fuse mean main power is dead main 12vdc power buss is dead. and that is much larger fuse even 100amps.
if you scan the PCM well that action will be dead. lacking PC power
so here is that power feed, battery must be 12.6vdc rested, not 10v
here we go ,2 paths dead, starter motor and PCM dead power.

Fuse link C blow out. GM gray coded,same goes fore Fuse a1/2 blown.
fuse link A, blown GM rust coded make alternator 100%^ dead and now the battery dead too ,lacking working ALT.
next is fuse link Z (GM gray) runs vast things.
I wonder what fuse is this PCM fuse as none are marked that.
there are 100 schematic to see, I am working throught them all to find PCM
are head lamps dead, are brake lamps dead?
head lamps work key off, so is always fix it first if dead.
fuse (Fa1/2 ) PCM/ABS fuse 10amps the a1 side is main power to this fuse. and this also kills dead the transmission range switch PRNDL and starter too dies.
So fuse A1 side is your critical failure point on this car.
so maxi fuse 40amps blew out from a short.
A1 FUSE GOES HOT KEY ON ONLY. (NO IMMO FAILURES IF HAS IT.
IF NOT a ign MAIN 1 FUSE 40AMPS IS BLOW
OR POWER TO MAIN ONE IS GONE.
mIAN1 IS WIRED HARD TO THE BATTERY MAIN
ALL MAXI FUSES ARE, SO IS BLOWN THAT FUSE OR THE KEY SWITCH IS BAD.(IN RUN)

With electrical issues, I usually pick one component that has a problem, then check the wiring diagram for that component. If that circuit is fuse protected, so much the better, then you check fuse circuit for voltage. Some fuse circuits are hot all the time, some go hot with the key on. If the fuse circuit gets ignition feed, meaning it goes hot with the key on, have to check feed to and from ignition switch.
Sometimes intermittent problems can be hard to track. Have to do testing when problem is ongoing.

Battery could not have crank power,I had three mouths old was done!!!

Well even a new battery can be drained down is you have something on all the time, in about an hour.

So start with checking for a drain.
Remove the battery cables in order to clean and grease them.
Then only put one on.
With everything off if you jump the gap of the cable that is off to the battery, with a test light, is should not light up. If it does, then you have a constant drain that will kill a batter over night.
You have to check for things like interior light, and disconnect everything, one at a time, to pin it down.

If you don't have a drain, then the next thing is to check continuity.
When you turn the ignition on, first the dash indicators come on.
The battery should read 12.5 volts.
Then you try to crank it.
The voltage should drop to 10 while cranking, and come back up after.
If it does not drop to 10, the starter is blocked and not drawing.
It could be the neutral safety switch, so try in neutral instead of park.
It could also be the ignition switch.
Use a test light to see of the small wire plugged into the starter solenoid (the small cylinder on top of the starter), get power when keyed to starter?
If it does not, then ignition switch or neutral safety switch.
If yes, then starter solenoid is probably bad.
But try turning the engine over at the alternator by hand or wrench, and try again. Could be binding between starter and drive plate.

Once you get it started, then rev the engine up and verify alternator goes over 14 volts, to recharge battery.
Otherwise battery will go dead in a day.

Then you should chaarge your battery and see if your alternator is good or bad. Hope this helps!!



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I think your starter went out not the alternator. chk. the starter.

Sounds like the battery is dead, you have just enough power to have the lights come on, but no cranking of the starter. Try putting the battery on a trickle charger, or hook up jumper cables to another car which is running. Let it run with the jumper cables connected for two mintues before you try and start your car.

Try this: Unhook the battery. Reconnect the battery. When the horn starts to beep, cycle the ignition key in the ignition on-off 5 times. This resets the alarm; the cycling of the key. Please advise me if this works for you.

the starter should be replaced. The solenoid is kikcing the pinion out but there is no contact being made to turn the starter motor. I have the exact same truck and before i changed the starter used the old starter tap trick. Tap the starter casing with a hammer and it should start turning again. hope this was helpful for you. Good luck.