My 1994 Xj12 is having issues with cranking over. I have checked the battery and it is good.
I have cleaned the terminals on the battery and the inside of the terminals on the cables.
I also cleaned the end of the ground cable that hooks to the body sheet metal at the side of the battery.
It shows over 12 volts at the actual battery posts but when I turn the ignition key to the on position, the volt gauge on the dash shows WAY less volts.
When I try the key in the start position the stater does not engage.
I had to move the car yesterday after it had sat unused for a few days.
I hooked a large heavy duty battery charger up to the battery by clamping over the terminal connections on the cables and switched the charger to a start boost setting.
At first this did nothing but eventually after two or three minutes the reading on the dash mounted volt meter jumped up to show over 13 volts and the starter engaged to turn the engine over when the key was turned.

Anyone have any suggestions? Should I be jacking the car up to look at the ground strap on the engine (wherever that is located)?

 

I would suggest that your battery has died, but you say you checked it? Did you check it with a load tester and it passed?

 

Did you check the contacts on the starter? It is looped in between the alternator and the battery so this could very well explain what you describe.

 

Batteries can read full voltage, but have no capacity. It needs to be load tested at a service center.

A simple analogy. 3” of water in a test tube, does not have the same volume/capacity as 3” of water in a bucket.