Got a problem with my XJ.
Every now and again it will not turn over after a short journey. Turn the key, everything lights up but nothing happens. No clicks or anything. Try jumping it but still nothing. Usually it will then decide to work if I leave it for 20 minutes with no issue?!?

Any ideas before I take it to a mechanic?

 

1. Try wiggling the shift lever or try starting in neutral when this occurs. If this allows the engine to turn over, your problem is your "neutral safety switch". A common failure on the XJ. Here is a link to refurbishing it, which often restores full function

http://go.jeep-xj.info/HowtoNSSrebuild.htm

2. Be sure all battery connections and grounds are good! Grounds can be the root cause of many electrical gremlins. Refreshing grounds is NEVER a bad idea!

You can't just check or look at these grounds. You must remove, scrape, clean until shiny the cable/wire ends and whatever they bolt to. The one on the back corner of the head, and where it attaches to the firewall. Scrape the paint from the firewall. Best to replace that woven cable with a #4 or #2 gauge cable. You can attach the one end to the intake manifold if you would like.

Next go over to the engine dipstick tube stud. Remove the nut and clean the wire ends and scrape the block until shiny at the stud. Reattach tightly.

If you are so inclined, add at least a #6 cable from the negative terminal of your battery to one of the bolts on your radiator support. Scrape the paint off first.

 

Just a quick thanks to you all.
Waggling the gear shift sorts it out!

Another quirk for "the brick"