Originally Posted by JCL

Essentially, engines only need three things to run: Compression, fuel, and ignition. Those things do need to be in the correct ratios, and at the right time, but that is it. Ignition is just spark. If you didn't have spark, you would flood it and smell fuel. An ignition problem could be anything from an ignition switch, to a control module, to a sensor, to the spark plugs. Ignition problems are far more common than fuel problems.