Originally Posted by rsantaniello
I have a 93 grand Cherokee 4.0 I went to start it this morning and it
hesitated then turned over fairly slow but started so I took it to autozone and had it checked they said the battery was bad so I got a new one Now this afternoon I went to start it and it turned over real slow Is it possible the new battery is bad Does anyone have any ideas
It helps if you have a voltmeter. A cheap radio shack $10 one helps.
Is this the original Mitsubishi starter, or has that been replaced, checked for excessive current? [They aren't hard to change, but don't do that yet]
You'll want to check the voltage at the two battery posts with the alternator running and battery hooked up. This makes sure your alternator is putting out.
There is one failure mode, an open diode, that is a bit harder to detect so if you get that far, you might want to have an electrical shop check charging.
Pull and clean your battery terminals and posts carefully. You want them nice and shiny.
There is a ground to the body near the battery. Take it off and make sure that connect is shiny as well, with no paint, grease, etc. on the body. Then tighten carefully.
If I recall, the voltage regulation is by the engine controller, not a built in on the alternator, so that COULD be going bad, but loose cables and grounds plague the ZJs.
After a good cleaning of every cable you can reach, put a good charger on that battery and leave it at least overnight. Then, measure the voltage.
Then turn your headlights on for 10 minutes and measure the voltage again, to make sure that your battery isn't taking a "skin" charge. [if you bought a good name brand battery, this is not likely, but good to check]
Then, you can have someone help you... put one lead of the voltmeter at the battery + post and the other lead where that cable connects to the starter.
Have someone run the starter for a few seconds and check the voltage you see.
Shouldn't be more than about 0.2 volts.
Checking current drain on the starter is a bit harder, at that point you might want to bribe someone before you swap it out..