I just got my 2000 XJ (4.0L) back from the shop and lo and behold there is another issue with it. It was in the shop for a coolant flush, inspection, engine knock diagnosis, squealing aftermarket brake pad ... you know, the usual.
It was finished last week and I picked it up on Saturday. The engine knock (which I was told was piston slap by two other shops; they said it was a lifter sticking) was noticeable quieter -- turns out they said the engine was low on oil [even though I just changed it less than a month before / check it every other week] so they changed the oil and put Engine Restore in as well. While I know many people have had good results with it on JF, I'm still calling it snake oil and was pretty pissed it was added without my knowledge.
I drive the jeep over 2 hours on the highway back for work. Runs fine on Monday. Yesterday evening is when I noticed it was struggling to turn over (low whee whee sound for a couple seconds); but when it did, it ran just fine. No low battery reading. The gauge read just past the line before the 14V mark. This morning, I get the machine gun effect.
I hooked up battery cables to a friend's V6 mustang and waited about 2 minutes. It turned over without hesitation. I let it run for 5-10 minutes and grabbed my multimeter. It read 13.90V. Take off the cables and wait another 5-10 minutes and read the battery again: 13.83V. It sounded fine [aside from the quieter engine knock] so I cut it off and waited a minute. Tried restarting the XJ and barely got it to turn over -- same whewue wheuw sound as last night. It sounded very bad. Super low idling (2-300 RPM) and rough lug lug lug lug sound. Battery gauge was reading the same as before. Gave it some gas, sounded a little better. Let off the gas and it almost stalled. I gave it some more gas (~1500 RPM) then let off the gas and it stalled on me.
Any ideas? My first thought this morning was a dead battery. Then I thought it was an alternator issue, but who knows with this thing.
Start with the basics. Determine if you have battery charging issues or connection issues. Jeeps do not tolerate low voltage, bad wire connections, or poor grounds.
Seems like a low voltage issue from:
• a failing battery
• a failing alternator
• dirty, corroded, or loose wire connections
• internally corroded battery wires
• leaving the lights on
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, the ground wires at the coil, and the ground wires from the battery and engine to the Jeep's frame/body. You must remove, wire brush, and clean until shiny the cable/wire ends and whatever they bolt to.
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 you 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. Load testing the alternator is still recommended.
Exchange the ASD relay with the Starter relay in the fuse box under the hood near the battery.
Have your helper turn the ignition key to START while you tap on the starter with a hammer. If the engine starts, you probably need a new starter.
Have the battery 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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I took the battery out while trying to reach for something else and figured I might as well test it. I charged it and let it sit overnight. Next morning the battery was reading 8.80V. I replaced the battery and the XJ fired up without hesitation.
However, I'm all-to-aware of the "if the battery dies like that, then your alternator may soon follow" saying. I was out running errands just now and figured I would at least see if the alternator may be acting up. The battery gauge was reading just above the mark right before the 14V midpoint on the gauge. I was at a red light and turned my A/C up to 3 (was on 2) and turned on my headlights. I sat there and just watched the gauge slowly go down and didn't go back up after a bit. I gave it some gas and the gauge went back to the previous mark very, very slowly.
Am I working with a dying-out alternator as well at this point? The belt is tight. It was tightened just a couple weeks ago during my state inspection. Terminal ends are clean.