Alright guys I've been on here a while and I'm at a loss as to why my jeep won't start. I just had to replace the alternator and now it won't even crank over. I'm getting power to the fuel pump and I've got 3/4 of a tank of gas. The battery has around 12 volts but I'm not even getting a crank out of it. Is there maybe some kind of security system or something where if it doesn't read the key right it won't start? All my accessories are turning on as well.

 

Did you try holding the key on start and jiggling the shifter in park and neutral?

 

Battery is fully charged at 12.65V, fully discharged at 11.8V. How "around" 12 volts is it? Charge it for a few hours, or jump it and go for a 45 min - 1 hour drive. That's assuming the battery is the problem and the battery is discharged.

Also, voltage isn't everything. All of your starting components need amps. Automotive batteries are rated in Cranking Amps, or Cold Cranking Amps if you in the north. No such thing as too much. A failing alternator can very often lead to the failure of a battery. Meaning if your alternator hasn't been charging your battery properly for the past few months, it may have killed it, unless the battery was new when the alt. started it's decline. Batteries in my neck of the woods typically last 3-5 years. So if you thinking you're close to that, then gear up and buy a new one before winter anyway. Preventative maintenance is the best, IMO. ;] Good luck! I hope you get it figured out. My XJ doesn't want to go right now either.