If a spark is not detected at the plug, what should be checked first?

When diagnosing a lack of spark at the spark plug, prioritizing the ignition switch is essential because it is responsible for enabling power to the ignition system. If the ignition switch is faulty or in the off position, it would prevent electrical current from reaching the coil, thereby resulting in no spark at the plug. Checking the ignition switch ensures that the system can function correctly and provides power to the necessary components.

Other factors, such as the flywheel key, compression, and condenser, are important for overall engine performance and spark generation, but they are secondary checks. A compromised flywheel key could lead to timing issues, incorrect compression could indicate a more significant internal engine problem, and a failed condenser might disrupt electrical storage and discharge in the system. However, these issues usually arise after confirming that power is being delivered to the ignition system through the switch. Hence, the ignition switch should be the first component to examine in this scenario.