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Starting trouble.

braeden

NAXJA Forum User
Location
Snowmass, CO
The other day a friend parked my car and must ahve left the key in the acc position as in the morning my battery was completely dead. I tried jumping it, but wasn't getting enought juice to get the starter moving. I hooked it to a battery charger for a few hours and the vehicle seems to have plenty of battery power, the door buzzser sounds normal, and the starter turns. The engine still won't turn over unless I give it gas and then it only runs as long as my foot is on the gas. As soon as I let off the tach dives and the vehicle stalls. I am hoping this is still a battery issue. The little window on the battery is dark rather than green, but I heard that is only 1 cell and doesn't mean anything.
Ideas?

Its a 96 4.0 AW-4
 
Most liquid batterys don't take well to being drained DEAD, older batteries are even less tolerant of it. The only thing I could suggest is leaving the charger on it for say 6 or 8 hours, trickle or low setting on the charger and see if it comes back, it may not. Deep cycle batteries are much more tolerant of this but cost alot more than the normal ones. Stick a meter on the battery and see what the voltage is...each cell supplies ~1.5v. Also batteries sulphate and the sulphur builds up in the bottom of the case shorting out the plates, happens in MC batteries that are left sitting all winter or snowmobile batteries that sit 3/4 of the year unused..
 
From my experience the '91-'96 electronics are very sensitive to battery issues. ANYTIME the battery goes dead the engine will not run properly when first started, even if the battery is fully re-charged and working fine. If you keep it running long enough for a short drive it may be fine. If your battery is in fact bad it may not get any better until you get a new battery. Might want to take the battery somewhere and have it load tested or if it's pretty old you might want a new one anyhow.
 
i jumped an xj one time that would run as long as the jumper cables were connected as soon as you took the cables off it would die, my opinion is the guys alternator was bad, it should stay running on its own current produced by the alternator dead battery or not.
 
I had it charging all day; went from -8 on the charger to -2. I got it started, but had to stay on the gas, otherwise the engine just died. Afterwards the charger read -8 again. I assume this means the battery is done. Hopefully this is an easy fix. Obviously I'm no elctrical engineer, but any ideas are appreciated.
 
I'm pretty sure joe88xj is right, if you can get it to start then the battery is supplying enough power and once its started the power from the alternator should be able to keep it running, battery or not. If after running the engine the battery is drained again, then something in your charging system is bad; alternator, ground, something. The first thing I'd do is check all the wiring and make sure it's all good, since thats a free and easy fix if it is your problem.
 
The reason your engine runs fine when your on the gas is becuase your alternator is putting out enough current to keep the voltage high enough to run the computer and ignition. Once you let off the gas and go back to idle, the alternator isnt putting out all that much power, and a wasted battery isnt enough to keep all the electricals running. I know this because my jeep is often used as the ouside stereo at parties, and with a sub and the system cranked to the max for hours, ive experianced this many times. Last time it happened I had to hold it at 2kRPM for 15 min before i could let it idle. A few months later it began getitng cold, and I couldnt start it after only an hour running the stereo. Got a new battery and everything runs great. almost 5 years with the old battery and lots of abuse. And I am an EE if that makes any diff
 
wrath has it right. A lot of the vehicles from around 1980 up will not run even if jumped with a dead or very low battery. The alternators don't put out sufficient charging voltage until revved up some. This is why the cop XJ's have a switch for extended idle. Try RichP's idea, it may help, may not. Also if it's not a maintenance-free, check the fluid level. Those batteries get sorta picky if the level is low and you drain them down on charge.

I've "brought back" dead MC batteries with this trick but it isn't 100%. Empty the battery. Pour a little coke in the cells. Shake. Empty. Repeat a few times. Flush VERY well with distilled water. Flush several times in fact. Refill and sit it on a charger overnight. This has worked for me in slightly over 50% of the times tried. *grin* Never had to do on my own bike as I ride it year round.

Sarge
 
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