Flooding causes. on 1993 Nissan Sentra

Turned key in ignition to start, the battery is strong, but it misfires. Tried numerous times throughout day, did not start. Kept foot off accelerator so I would not push pedal. Had it towed in and was told it was flooded. They cleaned everything out - no new parts - and it is fine. How does this flooding happen? Never happened before. Thanks.

Asked by for the 1993 Nissan Sentra
2 answers
Might be a cause of a week ignition system. I would have someone check out those ignition parts really well or put it on a lab scope.
Nissan fuel flooding was a $15 fix for me. It flooded on start every time, verify by pulling the fuel pump fuse, holding down the accelerator pedal and cranking. It will run for a few seconds until all of the fuel is burned. The fix is to replace the coolant temperature sensor. Replace the ECU sensor, not the gauge switch. The coolant temperature sensor fails, making the ECU think the engine needs rich fuel mix to start. It holds all injectors open which floods the engine.