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Unread 03-18-2013, 03:35 PM   #1
youarestuck
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Electrical prob. Stumped.

Hey All,
1998 XJ 4.0 - Automatic.
Noticed "spike" in voltage last week. Would run around 20 volts. Assumed it was bad ground. Checked all grounds, appeared to be fine. This happened a couple times, but the alternator has since been acting normal (14V).
Now the thing won't start. When I put the key in the ignition, it beeps as it should. When I go to crank it, absolutely nothing happens. Tried cleaning terminals. Tried boosting, nothing happened. Tried changing out the starter relay. All fuses are fine. Still sounds like a ground issue, but I could be wrong. Any insight or tips?? Thanks a lot guys

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Unread 03-18-2013, 03:58 PM   #2
CrawlingForward
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Wouldn't a ground issue cause a drop in voltage? (Actual question. Still learning electrical.)

Wouldn't that be a voltage regulator issue?
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Unread 03-18-2013, 04:03 PM   #3
youarestuck
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Quote:
Originally Posted by CrawlingForward
Wouldn't a ground issue cause a drop in voltage? (Actual question. Still learning electrical.)

Wouldn't that be a voltage regulator issue?
Yep, I think you're right. I wonder if the malfunction in the voltage regulator cooked my battery... But it should still start with a boost, no?
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Unread 03-18-2013, 04:15 PM   #4
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Have you tested to see if you're getting power at the solenoid when the key is turned? (I realize that probably requires an assistant)

You're not getting a clicking or anything? Perhaps it's an issue with the a relay in the fusebox? You might want to check that you're getting power at all the appropriate places there.
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Unread 03-18-2013, 04:29 PM   #5
CJ7-Tim
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The voltage regulator is inside the PCM and almost never fails. If you are seeing voltage spikes or voltage drops, you have a battery, wiring, or alternator issue.


Perform routine maintenance of the start and charge systems. Remove, clean, and firmly reconnect all the wires and cables to the battery, starter, and alternator. Look for corroded or damaged cables or connectors and replace as needed. Copper wires should be copper color, not black or green. Do the same for the grounding wires from the starter to engine block, and from the battery and engine to the Jeep's frame/body. You must remove, scrape, and clean until shiny, the cable/wire ends, and whatever they bolt to. Jeeps do not tolerate low voltage, bad connections, or poor grounds.

Place your DVOM (Digital Volt Ohm Multi-Meter) on the 20 volt scale. First check battery voltage by placing your multi-meter's positive lead on the battery's positive post ( the actual post, not the clamp) and the negative lead on the negative post. You need a minimum of 12 volts to continue testing. Next, leave your meter connected and take a reading while the engine is cranking. Record this voltage reading. Now connect your positive lead to the battery terminal stud on the starter and the negative lead to the starter housing. Again, crank the engine and record the voltage reading. If the voltage reading at the starter is not within 1 volt of battery voltage then we have excessive voltage drop in the starter circuit.

Typical voltage drop maximums:
• starter circuit (including starter solenoid) = 0.60 volt
• battery post to battery terminal end = zero volts
• battery main cable (measured end to end) 0.20 volt
• starter solenoid = 0.20 volt
• battery negative post to alternator metal frame = 0.20 volt
• negative main cable to engine block = 0.20 volt
• negative battery post to starter metal frame = 0.30
• battery positive post to alternator b+ stud = 0.5 volt with maximum charging load applied (all accessories turned on)

Test the output at the alternator with your volts/ohms multi-meter. You should be measuring 13.8-14.4 volts.

Have the battery, starter, and the alternator Load Tested for proper function in a test machine that applies a simulated work load. Handheld testers are inaccurate and will often pass faulty parts.
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Unread 03-18-2013, 05:06 PM   #6
NOTNSUV
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Had the same issue with my 99. Voltage would peg hi alternator checked out okay on TestBench. I replaced all the major wires battery to ground to starter to firewall to engine block. Has not happened since.
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Unread 03-18-2013, 09:20 PM   #7
youarestuck
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Update:

I checked out all connections with my multimeter (for a second time). Everything was normal. Still wouldn't turn over. Checked out battery with a real nice snappy batt tester I "borrowed" from the shop. All was good.
I decided to re-terminate the ground wires that connect to the battery. Also cleaned up the ground-to-frame connection.
Starts like a charm and runs 14.2V all day long.
Thanks for the help! Hopefully that fixed it.... Gremlins in the elec system can be annoying.
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