2000 XJ 4.0 stock. Weak cranking last week. It started but not in the quick explosive way it normally does. Then drove home from work and on shut down tried to immediately restart. No cranking.

I assumed it was battery (stupid of me) and went ahead and bought a new one and put it in. Cranked great again. Drove around a week no problems.

Today it sounded "weak" on start up again. Alternator right? I plan on taking it out and testing it at local parts store before purchasing new one.

What's the best way to take out. From the bottom or removing battery and doing it from the top? I'm leaning towards from the top as removing the battery seems easier. Anybody with experience with this?

BTW no check engine lights and no other symptoms noticeable besides weak cranking. I have not done battery removal test while running. Read conflicting advice on that and don't want to fry my electronics.

 

If moving the battery is your only obstacle, you will have better luck diving right into the project and seeing what works for you. If you still aren't confident doing the swap quite yet, check for a write-up or use a manual. I haven't done mine yet but is very strait forward. After you have everything tested obviously.

 

Keep us updated on your outcome. So, If you still are having problems we can work from there.

Good Luck!

 

DO NOT DO THE BATTERY REMOVAL TEST!

I assume you mean as some say disconnect the battery while it's running - if it stops the alternator is bad.
Than can ruin a good alternator and do damage to other components too.

Look at your voltmeter on the dash before you start it - once started if the alternator is working it'll read higher.

Before replacing alternator clean and check BOTH battery cables.

 

Well the car started fine after work. Before I started it, I read the voltage on the dash. It was at about 12 or so. Started kind of weak again but on first crank. Voltmeter climbed to just under 14 and stayed there. Not steady though. Kind of wavering +/- 0.5 volts.

I'm gonna sit on it a bit and see if the symptoms worsen before I take it out. Will update.

 

On my 88 xj the alternator was easiest from the bottom. It was in and out in about 30 min.

But I do think they slightly changed the location on the new models.

 

You can have alternator output tested at most parts stores in the parking lot.
From info you have given, I believe you have a prob w starter not alternator.

 

Pick up a can of CRC Lectra motive
Your local auto parts store should have it. Give your alternator and starter a good douching. While you've got the hood open you may as well check and clean all your grounds.

 

Thanks. I may try this before replacing anything.

 

Was 12, now 14 running - says it's charging.
The fluctuation - are the headlights flickering too?

Try it running and engine off - engine off replace battery.

Try measuring the voltage on the output terminal on the alternator - flickering there too?
Yes, replace alternator.

BUT FIRST - CLEAN AND CHECK THE BATTERY CABLES - BOTH ENDS OF BOTH CABLES! That's easily the major cause of charging system problems.

 

Haven't checked headlights for flickering. Will do so tonight in the garage. Seems to go from 13v to 13.5v when I give it gas in park.

Will purchase a voltmeter and check the output from the alternator tonight also. Thanks.

 

The more I read up on this the more I'm inclined to think its my starter like tgordan suggests. I'm going to take it apart and clean it as per this write up tonight and report back results.

http://www.go.jeep-xj.info/HowtoStarterClean.htm

 

It worked. Spent a couple of hours tonight but it was well worth it because it starts like a champ now. Strong.

Removed the starter and took it apart and cleaned every part with CRC lectra-motive electric cleaner. Used lithium grease paste to lube the gears. Put it back together and reinstalled it.

I've got a slow oil leak somewhere and oil had made its way into the starter, clogging up the electronics and gears.

I took some pictures and will do a write up and submit it for future XJers. But right now I feel great. I just wish I had done this before buying a new battery but oh well.

So for anyone out there with a weak and inconsistent start, first rule out battery and alternator. And if it's your starter, try cleaning it out before buying a new one. Saved $139!!