Novak Conversions Jeep Wrangler TJ engine mounts

Dead battery or water got in somewhere?

Succentor

TJ Enthusiast
Original poster
Joined
Mar 27, 2021
Messages
467
Location
England
TJ doesn’t get driven a lot, so I keep the battery on a float charger. Battery is 9 years old, though.

Last week I took it out - no problems starting, all ran fine. Got it quite wet and muddy on farm tracks with standing puddles - at times I had to go fast enough that the water splashed up over the windscreen but it was never more than 3-4 inches deep. Parked it for an hour, started up fine.

I wasn’t going straight home so I took it to a gas station jet wash to get the worst of the mud off. Stopped for an hour, it started but was a bit reluctant to start. Parked it up, put the battery on charge.

2 days later, my son went to start it and the battery was dead. Odd, as the charger said the battery was fully charged. Put it on a different charger which showed weirdly fluctuating voltage levels like it couldn’t decide what voltage to charge it at.

Dead battery all of a sudden (it is old, I guess, but absolutely fine) or did the jet wash get water somewhere it shouldn’t? If it’s the latter, where do I look first?
 
Do you have a multimeter to check voltage with the key off, and when trying to crank the starter?
Looks like you have a 2001, so your distributor is also a candidate for no start when it gets some water. Check that that's nice and dried out
 
Cranks but just barely. ‘Whomp whoomp…' then nothing

Yes, I do have a multimeter - what am I looking for?
 
Ok, so the battery is clearly FUBAR.

Before cranking: 12.1V. Turn ignition on, 8V. Crank, 3V…

Hopefully that’s it and there isn’t anything else nasty going on. Booked anyway for a service and MOT (inspection) in early January so they will replace the battery at the same time.
 
Novak Conversions Jeep Wrangler TJ engine mounts