If the starter turns but does not engage the flywheel, suspect that the starter is faulty.
Clicking and not starting is usually a low voltage issue from:
• leaving the lights on
• a failing battery
• a failing alternator
• dirty or loose wire connections
• internally corroded battery wires
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. 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.
Wiggle the automatic transmission lever in both Park and Neutral while trying to start. If it starts, you need to clean or replace the Neutral Safety Switch (NSS).
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, 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.
