Got a check engine light? Do you pat the gas pedal before cranking? That's a no no and can flood the engine. Smell raw gas? Had it been running ok lately? Remove a spark plug, inspect it for oil fouling. Put it back into the plug wire. Clamp a battery jumper clamp to the metal body of the plug and the other end to a piece of metal on the engine. Position the plug so you can observe the spark firing gap. Cover the empty spark plug hole with your finger. Get a helper to turn the ignition and starter. When the engine is spinning your finger should be sucked in on the intake stroke and blown out on the compression stroke. Everytime your finger is blown out the plug should fire with a blue spark.