91 XJ wont start

[mr2boy]

It started when it was -18, but soon as it got into the -20's, it would not start.  It turns over but wont fire.  I have checked for spark and that is good. Checked the distributor and it is dry and clean.  I replaced the plugs cause they were a little black, but still no go.  I have checked the fuel rail and its getting pressure when I crank it.  I have also sprayed starter fluid into the intake while cranking and it wont fire either.  I have had problems with my security system in the past, but the light would always be on when that happened, but now the light doesn't come and the horn doesn't honk when the alarm is going off.  Could it be something to do with the security.  I thought security would cut either the fuel or spark, but I have both.?

A mechaninc friend said I would have to take it to a dealer or somewhere where they have diagnostic equipment.  Does any one know a good honest place if that is the case.

Thanks

[Nickademus]

id suggest unplugging and plugging back in the wired just below your  ignition coil, the wires there can sometimes come loose or even break and ground out thus preventing enough spark.

orrrr, if you have spark, but still no vroom, id check your crankcase position sensor, the older cherokee's  seem to have  a problem where the harness for that sensor  gets old and  needs to be plugged and unplugged as well. the metal contacts can wear out after a few hundred k of vibrations.
that and metal shrinks in the cold.