No Power, No Start 87 XJ

Hi, I have an 87 XJ and i'm having a hell of a time diagnosing my problem. It all started when i was on my way home from work. I was getting off the highway and my autometer voltmeter started acting up. I thought it was the alternator because the headlights were dimming and the volts were dropping. So i shut my radio off in order to save my battery. After a few more seconds the volts dropped more and the headlights dimmed more. At this point i was almost off the highway. Seconds later my voltmeter dropped to zero and the jeep shut off. I had no power to anything. It has been like that for about 2 weeks and i cannot find out the problem. I have replaced the ignition switch which gave no results. The courtesy (sp) lights work as do the hazards. I probed the plugs and only one gets power (.69 volts). I am completely lost on this and i'm seriously considering putting a switch in to give power to everything and then a push-button starter. UGH! Any help would be appreciated.

Kinda hard to read between the lines, so I am gonna ask some basic questions so we can understand the problem better...Are you absolutely sure you have a good strong charged up battery with good connections at the battery posts? Have you checked all fuses, relays, and fusible links? Do your headlights work? Tailights? Brakelights? Radio? What works and what doesn't? Did you smell anything funny like smoke or a burning smell when it died? If you have a meter, what is the voltage at the starter?
Can you find a solid 12 volts in the interior somewhere? I'm wondering if you lost a ground connection.

dedo
that hapond to mine too i def think its a ground

you have power on the back side of the fuse box? I'm not 100% familiar with the wiring setup on these, but on the FSJ you had a corresponding connector on the firewall in the engine bay. if you have power there but not on the inside of the truck, you may try correcting the issue there.

Sounds like a toast alternator to me?

Voltage going down slowly until nothing is left...

Blaine B. said:

Sounds like a toast alternator to me?

Voltage going down slowly until nothing is left...

Click to expand...

me too, battery will run the vehicle for a while with no alternator

That's why I recommend a splash shield for the alternator at the very least. I paid the price once when wheeling. Some muddy water and my voltage slowly dropped until nothing was left. Somehow the engine kept running for awhile while I had no electronics what so ever.

On my dad's explorer, the alternator started to die as I was driving it. ECU shuts down everything that would take juice except for motor.

Do you have power to the ignition switch?
Do the gages move at all when you turn the key to run? Does that annoying buzzer buzz. Does the heater blower motor come on when the key is in run?
The yellow wire going to the rear of the alternator tells the alternator to start charging when the key is in run or start. No current no charge. If you are getting *no* current to or through the ignition switch the alternator won't charge.
The ignition switch is actually a stack of 4 (I think) switches, it's possible for one to be bad or two etc.
All the power to the ignition switch is from a single fusible link.

I had this problem with my 87 when the O2 sensor wires got too intimate with the exhuast manifold. The 12 volts to the HEGO O2 sensor heater pulled enough amps when grounded to do mine in. Nearly blew the fusable link. Check your O2 sensor wires for this. Then check the battery clamps and wires, and right near them there is a relay metal top, square about 1"x1"x2" with a wire leading to the battery positive post. When that relay dies nothing works. The wires coming off that relay have the fusable links, built in fuses that protect the wires from damage in case of a short. Check them next. Lastly check the big ground wire at the passenger side of the block near the oil dipstick.