Strange voltage behavior / no start

[AmbientMoto]

First post; this forum has been a huge resource with our first Jeep. We inherited an old Sahara and we love it. I've been going through it, replacing fluids, gaskets, transfer fluid etc. 2000 Sahara.

This morning it wouldn't start.

Turn the key, the dash lights up as usual and the volt meter rises to around 9 or 10, then drops suddenly and everything turns off. I connected the battery to the tender for a few hours, shows full but I'm getting the same behavior. Haven't had a chance to check the battery (voltage, cable integrity etc) etc but I thought I'd go ahead and post this in case someone has seen this and knows what the culprit could be!

Thanks in advance!

 

[Steel City 06]

Bad alternator? If you can get it to an auto parts store most stores will do free battery/alternator/starting testing.

It could also be a loose or corroded battery cable connection. Is there corrosion on the battery terminals? If so make a paste using baking soda and water and scrub it all off. You may have to disconnect the terminals to completely clean them.

Before hooking everything back up, clean all the terminals and battery posts with steel wool and make them shiny, particularly on any parts that contact. Also check the connections to the alternator post and to the fuse box in the engine bay.

Another problem could be a bad ground strap. In almost any car, the negative post on the battery is connected to the body or frame with a heavy gauge wire. If this ground becomes loose, corroded, or faulty it will cause what you describe, along with other problems. Check the ground wire on the negative battery post and check where it connects to the body or frame.

 

[TJBrad04]

You need to have the battery load tested for amperage capacity, voltage only tells half the story. Any auto parts store should be able to do that for you.

Sent from my Pixel 3 using Tapatalk

 

[Steel City 06]

I misread your post. I thought the engine started and then shut off.

Can you jump the Jeep on another car? If it starts up without issue then it’s probably the battery. Unlike the battery tender another car should be able to provide enough amperage to start a car even without a functioning battery.

If the battery is not holding a charge it is probably internally shorted and needs to be replaced.

A group 34 battery is the stock size battery. A group 24 is a little taller and higher capacity but fits without modifications.

If you can afford it go with an Absorbed Glass Mat (AGM) battery. They can withstand significantly more abuse than a flooded cell battery.

 

[AmbientMoto]

Completely forgot to wrap this up... it was a simple thing... my negative terminal was failing; I had tightened it a while back so I didn't suspect it. Old age had caught up to it. Easy fix.

More important... even though this is very late... thanks so much for the responses!

 

[Steel City 06]

Glad you got it fixed. Welcome to the forum!