It has happened a few times where it does nothing and after a few tries it fires up normally. I have read all the threads on the NSS cleaning, bypass, etc. but I am a retired auto tech and I would like to see exactly what's going on before I randomly replace parts or take something apart to clean it, etc. I have a clue that it is likely on the control side because the cover is off of the starter relay and I'm guessing it has been started by closing the contacts there by the previous owner during a no start condition but I have never had a complete failure where I couldn't start it so I can test it.

Does anyone know where to get a schematic of the starting system that includes ignition switch, relay, nss? The entire circuit. Most cheap manuals don't have good schematics, any place to get a "real" manual for an XJ? I'm guessing I will need one down the road, lol.

 

When the problem occurs, does cycling the key back and forth help? That would tend to point to the relay or less likely the ignition switch. Versus having to wiggle the shifter or put it in neutral pointing to the NSS. If you backup lights don't work, it's almost certainly the NSS.

 

I cleaned out my NSS due to the reverse lights not always working, so decided it was worth doing before it caused a no start. If it's an original it's probably worth cleaning regardless of your fault cause.

I've also had my original starter fail which caused intermittent no starts on me.

 

The easiest test is to keep the key cranked and cycle through Park > Neutral, if it starts every time The NSS is on its way out, they get worse.

As another poster mentioned, if its an original OEM switch, they get very oxidised,

I have repaired them on various makes and models, some older ones are vey hard to come by and/or expensive

I have done a couple on XJ, they need a good clean and polish on the copper, careful not to break the plastic getting them off the shaft

 

It came apart very easy. The grease was so hard and sticky inside the springs, when I pushed the contacts down and compressed them they barely sprung back at all, it was like slow motion. Cleaned and lubricated with dielectric grease and all seems well.