Searched multiple threads and forums with no joy on finding a solution. This was a big help for me too.
https://www.cherokeeforum.com/f59/no-start-checklist-155216/

Background: few days prior to this issue, I had replaced the fuel pump, plugs, wires, cap, rotor, and cleaned the TB for a tune up. Worked great and started up faster than prior to the tune up.

Current issue: Few days later. I'm driving home from a junkyard and notice a rattle coming from under the motor that kept in line with engine speed. By the time I had gotten home, noise went away and when I checked under the vehicle I believe it was something hitting the exhaust near the cat.
Hours later when I went to start the car, nothing. No crank, no click...just silence. At this time, neither a jump start at battery nor the starter turned the motor over. Same response in Park and Neutral.
Following day, I remove and replace the starter. No joy from the key turn BUT I can arc start the starter. Thus leading to the ignition switch. Ignition switch is replaced and no change at either point.
Frustration kicks in. My neighbor buddy is a mechanic so he helps me out with a multimeter. Reading from the battery is low at 10.3. I took it for a drive, via arc start, to see if it would charge up more seeing as it's been sitting for 2 days and using power to test. When I got back, took a reading and it was the exact same. Battery perhaps?
Following the check list above I looked at fuses #19 and #10. Fuse 19 in the kick panel was blown (good sign?). I swap another 10A fuse in, reset the battery...still silence on turn key and arc start still working. We take the meter and read #11 and #19 In the kick panel...11 is good but I'm getting a 0 reading from the 19 fuse itself and at the fuse slot (with ignition switched to ON).
Other items to note: all relays and fuses in PDC are tested and working, grounds and terminals have been cleaned...
Thoughts from anyone? What did I miss?
I know someone will say something about the NSS but having cleaned it just a couple months ago and the inability to start in neutral as well leads me rule it out.
Input much appreciated.

 

Someone will say something about the NSS. Mostly because a starter that will arc start combined with a brand new ignition switch with no change has the hallmarks of an NSS problem (Starter Motor Relay and Starter Solenoid are probably still in play as well). I would recommend you jump the NSS at the connector to rule it in/out to at least remove it as a variable. Another user just yesterday had a similar set of symptoms, and had recently cleaned their NSS. So they did not suspect it either, but ultimately it was the NSS (or at least that was the last update they posted). So don't rule it out, unless it is really ruled-out. To jump the NSS connector to test shouldn't be very time consuming.

 

Fair enough. I was not aware you could jump or bypass the NSS. I frickin hate electrical diagnoses.

 

NSS bypass did not solve problem in any gear.
also of note, reverse lights still turn on as they should.
what's next?

 

Good, now you can rule that out. Worth doing.

What's next is to troubleshoot the starter motor relay to figure out what item is missing in its equation. The control side of the relay gets its + from the ignition switch, the ground from the computer, the load side of the relay is + and comes from the PDC via the fusible link (basically from the battery). If the control side + is missing when attempting to start it means there is a problem between the ignition switch and the relay. If the control side ground is missing it means the problem is between the PCM and the relay. If the load side is missing its + feed that means the PDC and/or fusible link connections back to the battery might be suspect. By control side I mean the coil side (where positive and ground come together to activate the relay), by load side I mean the part of the relay that carries the main load to the component it is activating (in this case the starter motor solenoid).

On the XJ starter relay you can generally quickly tell the difference between the control and load pins/sockets because the control side pins will be the smaller ones, and the load pins will be slightly larger.

If you can arc start the starter directly, and if you detect 12v+ on the starter relay load, I think I might next try to jump the load on the starter relay, which would energize the starter solenoid and cause the starter to engage. If there was no action there it might lead to suspecting the starter solenoid (since we know the starter motor itself is working), or at least a problem between the relay and the starter solenoid. If you have any confusion what so ever as to what it means to jump the load pins on your starter relay, then do NOT do this, because if you accidentally jump the 12v+ load to the grounded PCM control side socket - you will likely fry your PCM. Google "diagnose starter relay" for more information.

You can also google "how to diagnose a no-crank condition". Because the general approach tends to be the same for most vehicles.

 

Yup good call on the relay jump. Ended up finding a video where pin 87 on the relay was grounding out due to poor connection at the S post. Hooked up my meter and sure enough, same thing. With the meter still set on the + batt and grounding on 87, wiggled the wires around the near the starter connection and presto, she fires up.

 

Bam! Awesome. Glad you got it.

 

Appreciate the help. I hate when it's stupid stuff like this that causes such a fuss.
Anywho, gotta figure out how to A find that same part or B just splice on new wires and hole ends to make the connection.
might as well do both while I'm there.

 

Maybe I'm not done.
Hooked up my test light to check the loads on each pin. Results as follows.
Pin 85 - ground is constant
Pin 86 - edit: lights on key turn, not on arc start
Pin 87 - constant light when grounded via + batt, will light via arc start when grounded and powered
Pin 30 - no light on key turn or arc start, no ground or power

EDIT: so not receiving any power to pin 30 leads me on a hunt. Under the box, 30 has a black with pink wire running to the 30a fuse in the PDC. From there, another black with pink wire runs into the mess of other wires that lead out of the PDC to which I cannot find where it ends up. No diagram has helped me yet.
Does anyone know where this wire leads? If I'm learning this right, if pin 30 isn't receiving power then it cannot switch power to pin 87 via ignition, hence the "no light" on 87 when key is turned.

 

30 should be going to the starter solenoid. It would be dead (not energized) unless the relay is engaged (circuit closed). When the relay closes it would send the battery + from pin 87 to pin 30 then down to the solenoid. I don't have my diagrams in front of me, but I think the solenoid gets its positive from the starter relay (pin 30) and its negative (ground) from the ignition switch (that's the part I'm a little unsure of, but would mean that jumping the relay might not work if the ignition switch was not in the start position at the same time).

 

Son of bi*ch. Wife called and said her 99 Cherokee wouldn't start. Tried the "take the cover off of the starter relay and press the side to make the connection". Started right up. Guess I'm putting in another cylinder start mechanism. Putting the part number here in case I ever need yet again. Dorman 924-704 Ignition Switch Actuator Pin Compatible with Select Models
If you have never replaced this part on your XJ, I would recommend knowing how to use this mechanism to bypass the ignition key. You will need it eventually. Or just replace it because it will break.