1992 Range Rover with only one spark and won't start - how do I fix it?

I own a 1992 Range Rover Classic 3.9 County Edition. I have replaced the distributor and ignition component, but still only one spark and won't start. I have been told to look at the distributor and crank sensor, but the distributor is new and the vehicle doesn't have a crank sensor. Has anyone encountered this issue or has a theory on the problem? Where should I look or what system should test?|||What about your ignition coil? Have you tested that?