Another Jeep was running, then wasn't running thread

TreverStevens

TreverStevens

Knows enough to be dangerous
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So I got my project TJ of almost 3 years running about a month ago. Since then I’ve been ironing out various things here and there (mostly steering and ride quality issues). I’ve put about 300-ish miles on the engine since the swap. Today I readjusted my caster because it was off from swapping in new UCA’s/LCA’s on the front and got it to about 6°. Needed to run a quick errand so I took the Jeep for a shake down. About 10 minutes into my ride, doing about 70 on the highway I lose power. Engine: gone, dash: dead, stereo: dead. I try cycling the ignition a few times while still coasting with nothing. No clicks, nothing on the dash, everything’s dead. I pull over to the shoulder and try the ignition again, no luck. I pop the hood, check battery and terminals, everything is connected and battery sitting how it should be. I give a quick check of the connectors to the PCM, all seem tight. I check the connectors in the driver’s side footwell because I did a dash swap last week and had to unplug some of those, still no luck. I’m bamboozled and called for a tow home. Since I went through my insurance roadside assistance they kinda balked about having it towed to my house instead of a shop, but it’s at my house now. Oil was a little low so I added a quart and still nothing. I put a charger on the battery and it came back fine.

Any ideas what this could be or where to even start to isolate the issue?? 1997 SE with a 5.9 Magnum, NV3550.
 
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rasband said:
This seems like a good place to start, either the battery or alternator.
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Alternator is brand new from the swap. Not even a year ago I installed it and less than a month of the “new” engine running now. My voltages were all fine and dandy yesterday while out driving. And nothing indicating bad electrical prior to it dying on the highway?
 
@Wildman @MagnumV8 do you guys or any of the others with the Magnum have any ideas? Is it possible my PCM just crapped out suddenly? Because I can’t get anything on the dash to respond when I cycle the key. I figured my radio should at least come on even if my battery was low?
 
TreverStevens said:
Alternator is brand new from the swap. Not even a year ago I installed it and less than a month of the “new” engine running now. My voltages were all fine and dandy yesterday while out driving. And nothing indicating bad electrical prior to it dying on the highway?
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Given the means of getting it started again, it seems worth double checking.
 
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TreverStevens said:
@Wildman @MagnumV8 do you guys or any of the others with the Magnum have any ideas? Is it possible my PCM just crapped out suddenly? Because I can’t get anything on the dash to respond when I cycle the key. I figured my radio should at least come on even if my battery was low?
Click to expand...

If I understand correctly you have no power to ANYTHING? Dash doesn't come on when you turn the key to run?
As rasband said I'd start with the battery and verify that you have 12V.
Do you have headlights?
If not it sounds like a ground issue. Did you build the wiring harness yourself?

Start at the basic. Verify your voltage at the battery first.
 
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So I have 11.92v at the battery. The only function I can get out of my Jeep is the hazards can come on and my headlights/taillights. Where’s the ignition switch connector? I checked all the connectors under the dash in the driver’s side footwell and everything is snug there. All my connectors to the PCM are snug too.
 
TreverStevens said:
So I have 11.92v at the battery. The only function I can get out of my Jeep is the hazards can come on and my headlights/taillights. Where’s the ignition switch connector? I checked all the connectors under the dash in the driver’s side footwell and everything is snug there. All my connectors to the PCM are snug too.
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That voltage pretty firmly in the low charge category for a battery and can be the kiss of death. I'd bet if it jumps easy you know the issue (the battery).
 
rasband said:
That voltage pretty firmly in the low charge category for a battery and can be the kiss of death. I'd bet if it jumps easy you know the issue (the battery).
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So even at that voltage it’s normal to not even get the radio to or gauges to show anything? In the past when I’ve had a battery go out, I can at least get the radio to power on shortly or get my dashboard to light up.
 
TreverStevens said:
So even at that voltage it’s normal to not even get the radio to or gauges to show anything? In the past when I’ve had a battery go out, I can at least get the radio to power on shortly or get my dashboard to light up.
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Do you have another vehicle? You could easily find out by testing a known good battery. But I've seen various different things not work depending on the vehicle.

I'm not saying 100% its your battery, but it seems likely and easy to test.
 
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Ya, my other DD is an 04 Cummins. I was going to try jumping the Jeep tonight but the mosquitoes are out in full force tonight and after already spending an hour out in the yard I didn’t want to deal with them anymore. I’ll try jumping the Jeep tomorrow. I might even just pull the battery and take it to the parts store to have them test it tomorrow. I got it tested about a month and a half ago because my battery tender wasn’t putting a charge on it and the display was saying bad battery. O’Reilly’s charged and tested it, they said it came back good. The battery is from 9/19, but was only used about a month before my engine went out and my 2.5 year project started on the Jeep. I’ve had it on a tender most of the time during the project.
 
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TreverStevens said:
Ya, my other DD is an 04 Cummins. I was going to try jumping the Jeep tonight but the mosquitoes are out in full force tonight and after already spending an hour out in the yard I didn’t want to deal with them anymore. I’ll try jumping the Jeep tomorrow. I might even just pull the battery and take it to the parts store to have them test it tomorrow. I got it tested about a month and a half ago because my battery tender wasn’t putting a charge on it and the display was saying bad battery. O’Reilly’s charged and tested it, they said it came back good. The battery is from 9/19, but was only used about a month before my engine went out and my 2.5 year project started on the Jeep. I’ve had it on a tender most of the time during the project.
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Try to get a charge on it before you bring it in, when I worked at autozone we wouldn't run the test on a battery under 12.6.
 
So I put the battery on a tender for a day and a half. It was reading 12.88, I installed it back in the Jeep and still get nothing.

Is it possible my PCM just totally crapped out?
 
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