So, yesterday I tried to start my Jeep during my smoke break to listen to the radio. The battery seemed drained, so I used my battery pack to crank it up. It started but then it died after it idled down. I thought maybe it was my alternator, so I used the battery pack again; the jeep started and I was able to put it into reverse (so that I could drive around to charge the alternator) but soon as I pulled out of the parking spot it died again. I used the battery pack for a 3rd time to be able to put it back into the parking spot. Afterwards, I waited for 2-3 minutes and just tried to start the vehicle without the booster and it started right on up. So, I then proceeded to drive the truck around the building of my job to charge the alternator. I parked it and turned the vehicle off, but it would not start again?? When I left work I used the battery pack for the 4th time. I then drove it back home and this morning it would not start back up for the life of me. I used the battery pack again but nothing, I asked a neighbor for a boost, nothing. The neighbor was kind enough to drive me to Walmart for a new battery. The customer rep proceeded to tell me I had the wrong battery for my Jeep and didnt want to honor the warranty. I bought a brand new battery for $163 dollars and the Jeep won't start still.

Does anybody have any idea as to what the problem is? I forgot to mention that on the drive back home yesterday, my "check gauges" light came on due to the battery charge jumping from 14 to 19. Any suggestions of the problem would be super helpful. Thanks

 

clear all codes by shorting the battery cables together for 30+ secs to clear all codes

see what happens then

test for spark at plugs

does the fuel pump whir for 3 secs with ignition key "on"

My XJs always need throttle if jumped, as the dead battery pulls so much charge that the PCM and sensors dont get enough voltage

One way around this in an emergency is to disconnect battery and run with jump pack alone in its place

I have a book sized 1000CCA lithium jump starter

 

What condition are the battery terminals in? When it does run what kinda voltage level is the alternator putting out (use a meter for this vs the gauge on the dash)

 

IIWY I'd pull out the alternator and have it tested (usually for free) at AZ, Advance, etc. IMO the alternator got a major malfunction and you're risking doing something bad to the PCM by leaving it in there to test stuff.

 

Also consider bringing the starter along too.

 

Is the starter engaging at all? If you're cranking and nothing is happening, check fuel/electric. If you turn the key and nothing happens, and you know the battery is charged, check the starter or the Crankshaft Position Sensor. Even if its screws are a little loose, the jeep will die randomly.

 

I had an early XJ when I moved to Wa State in 2001. The starter was slowly giving up the ghost. Eventually I had to smack it with a mallet to get it to turn over. I did this one time too many times without replacing the starter and it left me stranded. A new starter fixed my problem.
74Plb