G'day I'm a newbie so be gentle..

I've got a problem with my 3.5 TJ, on turning the ignition to start it, all the instrument lights on the dash go dead and there's nothing. It happened a couple of weeks ago. I disconnected the battery for half an hour and reconnected and it started.

It happened again this afternoon while my missus was at the servo. She did the battery disconnect thing and it started for her.

Any ideas? I thought it might be the immobiliser. There are no fault codes coming up on the dash. When it starts normally it cranks over really strong and fires quickly. Many thanks.

Dud battery or corroded battery lead.

Thanks MadMax for your reply.

I had a suspicion it might be the battery, but I kind of ruled it out cos it fires up really well most of the time.

Next time it does it, and wont start, let it sit switched to ON for about 20secs before cranking?

Dads KJ did had an issue like that. Ended up replacing the battery and it fixed it.

Cheers lads for your advice.

I had a suspicion it might be the battery, but I kind of ruled it out cos it fires up really well most of the time.

Not so common now, but a battery can develop a break in the internal connections between cells and be good one second and dead the next. And then decide to go good again.
Next time it does the no start thing, give the battery terminals a pull and push, and try to start.
I had one battery that did that intermittently and I carried a spare battery around in the car - not very safe I know. Took six months for that one to fail permanently.

Of course, it could just be dirty battery terminals. Always best to start with the simplest, cheapest and quickest potential fixes first. lol

Happened to me once a few weeks ago, figured its the battery cables.

Started car, worked perfect, stopped to use ATM, got back in car, turn key, all lights died and no ignition. Got out and took the Neg cable off the battery and put it back on, car worked fine and hasn't happened since. Assume its corrosion on the other end of the neg cable or something? I will have to go actually look :P

Looks as though it was the battery terminals/cables. I gave them a good clean up and it hasn't happened since.