It's a 1989 Jeep Wagoneer. As is the case whenever there is no spark being produced by the spark plugs, the engine cranks but just doesn't start. I've replaced the rotor and distributor cap, and cleaned the bottom of the cap with a nickel. When it comes to the distributor, ignition coil, and all that stuff I'm not too sure what exactly I'm doing, which is why I'm posting here to get others' advice. Any suggestions? Any help would be greatly appreciated.