I have a 2000 jeep cherokee 4.0 that will not start. Here’s the mystery- the battery and alternator are brand new, battery checks at 12.4v, and the wiring from battery to alternator and starter are heavy duty cables replaced last summer. HOWEVER- when i turn the key, there is no power, nothing, but when i connect the battery to jumper cables, everything works, but barely cranks and then clicks. I am so confused and any help would be greatly appreciated.
Clicking and not starting is usually a low voltage issue from:
• dirty, corroded, damaged, or loose battery terminal or wire connections
• internally corroded battery wires
• a short circuit or parasitic drain
• a failing battery
• a failing alternator
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. Battery terminals and battery wire connectors should bright silver, not dull gray/black and corroded. 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 onto.
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.
Jeeps do not tolerate low voltage, bad wire 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 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)
Have your helper turn the ignition key to START while you tap gently on the starter with a hammer. If the engine starts, you probably need a new starter.
Check the battery, as CJ7-Tim advised. Lead acid cells can sometimes do strange things. It's possible that one or more of the cells in your battery are going negative when loaded. It's a very strange thing to see. The voltage in the cell will be "normal" (2.23-2.25 volts nominal) when unloaded, but will immediately switch to close to the same voltage with swapped polarity (-2.23- -2.25 volts nominal) when a load is applied. Then, when the load is removed, it will change back to normal polarity. This situation will pull any power source you apply to it way down, as the faulty cell(s) basically negate an equal number of good cell(s). A 12 volt automotive battery has 6 cells, at 2.23-2.25 volts nominal per cell, for a nominal total of 13.38-13.5 volts. One bad cell will lower that to 8.92-9 volts nominal. Two bad cells nets you 4.46-4.5 volts nominal. This is easy enough to check for with nothing more than a volt meter. Check unloaded battery voltage, then loaded (key to start) battery voltage. You WILL see some voltage drop under load, the question is "how much". If it's falling to high 8s or lower or low 9s under load, you very possibly have a bad cell in the battery. If its only falling to the high 10s or low 11s or higher, check your starter.
Short answer: Investigate the Neutral Switch attached to the tranny. ( If you have an automatic.) EVERY Jeep XJ automatic tranny owner needs to know about that thing.
Possible internal short on your battery.
My 1988 XJ has had issues with the neutral switch attached to the transmission. Needs internal cleaning. That'll give you absolute zero voltage. Mines an Automatic. If you have an automatic try messing with the transmission control lever. Moving it around. That's what I do when it acts up till I can get under and clean it up inside. It'll shut you down cold. The JUMPER angle is weird. You could have an internal short in the battery.
I've spent countless hours keeping this old thing going. Studying the service manual.
The symptoms don't really make the Neutral Safety Switch (NSS) a likely suspect. NSS problems typically result in no action from the starter, even if jumper cable are applied to the battery.
The clicking sounds are a primary symptom of low voltage. The battery, starter, and the alternator should be 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.
Check your fuses , and your starter relay, maybe swap it out with another . Try a jumper wire were the starter relay goes, pin 87 to pin 30, with key in run , see if it starts . (if swapping relays dont work).