I've been thoroughly researching old threads before posting this so i've come prepared... My 98 XJ is not cranking when I turn the key and I've isolated the problem to either the NSS, the ignition switch, or the wiring.
I know this because I can start the engine no problem by jumping pins 30 and 87 on the starter relay. However all of my diagnostic tests are suggesting BOTH the NSS and ignition switch are not working. I find that hard to believe...


So the NSS feeds a ground to pin 85, the ignition feeds power to pin 86. Seems easy enough to isolate, right? Here are my latest tests:

• I know my relay is good. I get continuity between 85 and 86. After hooking up pin 85 to battery ground and pin 86 to the battery positive, there is an audible click from the relay and i get continuity between 30 and 87.
• I tested every fuse in the PDC. I get continuity with all of them. I tested F19 in the junction block. Continuity there too.
• With the relay unplugged, hooked up pin 85 to the 85 cavity with a jumper cable. Hooked up pin 86 to the battery positive. No click. That suggests that the NSS is not providing a ground.
• With the relay unplugged, hooked up pin 85 to the battery ground, and pin 86 to the 86 cavity. With my helper turning the key to crank, the relay makes no click. Now this is suggesting that the ignition switch is not providing power.

Is this possible? Of course, but it's gotta be unlikely. Do my tests make sense? Is there anything I'm missing here? I've been chasing this for 4 days and it's driving me nuts!

 

Does the relay click with the key turn when the relay is installed? What about when you put it in neutral? Do your backup lights work?

You're correct that jumping pins 30 to 87 should crank as it bypasses the relay and the NSS. However, when you energize the relay (pin 85 & 86) you should also get continuity across pins 30 and 87. Did you check that while you had the relay out?

Below is the pinout for the NSS connector. Pin 7 and 8 make contact in P or N. You can check for continuity on the NSS side in P or N. You can also jumper across them on the harness side and try to crank.

 

Forgot to add, you can try swapping the starter relay with one of the others in the PDC, like the radiator fan or even fuel pump to verify it's not the starter relay.

 

Backup lights are working. With the relay energized, i get continuity between 30 and 87. With the jeep in park, I get continuity between pins 7 and 8. I also tried jumping the NSS on the other side to no avail.
Also tried swapping the relay. No matter what I do, other than send direct ground and power to 86 and 85, i cant get the relay to click.
so now I'm leaning more towards the ignition side of things. what else can i test?

 

Just for clarity, on the starter, the solenoid has 3 terminals. Two big ones and one small one. One big one has your battery cable attached. The other big one goes to the starter motor. The small one comes from the relay and energizes the solenoid when you turn the key to START. The solenoid engages and drive the bendix out to engage the flex plate and connects the battery and motor posts.

On the NSS engine harness side, check for continuity between pin 8 and ground.

Below is the pinout for the Starter Relay in the PDC.

Since jumping D10 and D14 (87 and 30) cranks, there should be no issue on this side of the circuit.

D11 goes through the NSS so check for continuity when in Park/Neutral.

D13 gets power from Fuse 19 in the Junction block. Fuse 19 gets power from the Ign switch when key turned to START. So I would pull the fuse and check for 12v with the key turned to START. Not sure which side of the fuse so do both. If nothing, then I'd guess your ignition switch is bad (or possibly the wiring). If good, then check for 12v at D13 (Key to Start). If nothing then the wiring has an issue.

One last thought, do you live in a rural area? Is it possible rodents may have made a home in your XJ?

 

I assume you've tried with the shifter in neutral. This is where a test light is helpful. Use your meter and measure the resistance from ground side of the coil to ground, also check the hot side back to the battery. You're looking to see if it's high resistance. Just seeing voltage can be misleading.