YJ: Starting Problem

[TipsE-Z]

So... I've finally ran out of ideas. As some of you know I work in electronics and micro processors so I'm not totally lost when it comes to electrical issues; but now... I'm confused.

My Jeep just started, suddenly and without warning, turning over real slow as if it was freezing cold (I live in Az) or the battery was low. I checked the battery with my meter, good. I checked the alternator while it was running and it showed good. I figured I was just losing my mind and left it alone for a bit. Fast forward two weeks of the Jeep running good and hear we are. I drove home from work Friday, parked it, Saturday it wouldn't start. Here's what all I've checked:

Battery connections - cleaned, electrical grease applied, tight on posts
ALL cables in starting/battery system - removed, cleaned, contacts cleaned, tightened down
Battery check by Autozone; checks good
Alternator checked by Autozone; checks good
All sources of power draw, except cb and starting/running fuses are disconnected
Starter relay checked with meter - good
Ignition relay checked with meter - good
Still no start...

Got the battery on the charger now, going to give it a go later, I drained it down a bit trying to get it to turn over. I know it isn't a fuel issue with the slow rate it turns over.

Another note: It once had a security system; I removed it the day I brought it home and have never had this issues until recently. Any help would be great!

[6spdYJ]

Although it may have checked good looking at volts, that doesn't mean your plates aren't eroded or your acid isn't weak. To truly test the battery, you would need to have an ammeter in series with your starter to see if it is delivering all the current necessary to crank it fast enough to start. Just for giggles, try it with a known good batttery.
The starter motor bearings may also be shot, or the windings may have opened.

[aw12345]

Measure cranking voltage, or even better cranking amps. Have the battery tested, or crank it for a good 30 seconds with the ignition disconnected and see how voltage holds up. It's either the starter or the battery if you tested all battery cable connections for voltage drop while cranking

[Russ Chung]

A quick test to determine if it is the battery or the starter is to crank it over with the headlights on. If the lights get very dim, it's a sign of a weak battery. If the lights stay bright, it is a sign that the starter is not drawing enough current.

[Ol Man]

What they said. It sure sounds like a bad battery, especially since you cleaned the terminals.

[vwtipeii]

I know nothing about this either but my jeep whet from running fine to running like crap in a day. Wo orgiinally thought it was the fuel pump, so we put in a new one (not a bad idea anyway since it was the original one from 1994) and still had the issue. Jeff B. figured out it was the crank positioning sensor. Runs like a top now.

Also, before the CPS was switched a few months ago my jeep would turn over on a full charge and just not fire... finally my mech replaced the ECU and it started again just fine. ECU's aren't cheap.

Best of luck.

[TipsE-Z]

Thanks for all the help guys. I have had the battery load tested at Autozone. After a bit more thought (and beer to aid in thinking) I really do agree that it's something in the starter. The Jeep will bump start just fine, and while it's running it shows good voltage. The alt meters out good current and voltage. The battery meters out a solid 14.2. The wires all check good for continuity (I measure this in Ohms, easier to spot frays/nicks this way). I haven't even give an ECU a thought, I'm going to pull the starter on it tomorrow after work and get that tested.

To be honest... I'm thinking this could be a great time to start cleaning everything up on it, and do some build work. The rains are coming to Az soon I'm told, and so is the 110 degree heat. I'm too lazy to put the top back on for the rain, and WAY too lazy to put it on for the rain then pull it off for the heat. I have no A/C so even with a bikini top and no doors it's pretty toasty. Think this could be a sign to start detailing things up and putting some of the parts on that I have laying around.

[Old Fart]

Were any of the terminal ends corroded? The corrosion can creep into the cable, severly limiting ampacity - and cleaning the terminals won't cure that. They'll pass a continuity test just fine - just won't carry a load.

[TipsE-Z]

The terminals were relatively clean. I wouldn't call them corroded. I had an idea yesterday (haven't worked on it yet thanks to the J O B); maybe the starter solenoid is bad? Like it isn't fully shutting off, thus why my amperage fluctuates while running and the starter doesn't fully engage because the spring isn't getting energized as it should??

[6spdYJ]

Acid can flow up the cable several inches and give no indication at the terminal that the cable is actually shot. Take the cable off and bend it aggressively down the whole length with your hands about three inches apart. If it feels crunchy or suddenly soft, get a new cable. It will also do it on the fusible link.

[TipsE-Z]

Well... The verdict is in! Bad starter. The gear would engage the fly wheel but the coil wasn't able to continuously pull enough current to turn the load. I learned that Autozone gives a military discount this morning as well; FYI for those who didn't know. I'm off to do a trail with my dad to test it out, but the Heep starts better than it ever has before Thanks for the ideas folks!