What does cold-start enrichment do?

• A. Reduces fuel during cold start
• B. Increases fuel delivery during cold start
• C. No enrichment during cold start
• D. Increases fuel delivery after warm-up

Answer: (B)

Cold-start enrichment is about delivering more fuel when the engine is cold so it can start and run smoothly. When the engine is cold, vaporization is slower and the mixture needs more fuel to reach the right air–fuel ratio for ignition. The fuel metering system temporarily increases the fuel delivered (via a cold-start circuit, injector duty cycle, or a dedicated cold-start injector) and then reduces it as the engine warms up. That’s why increasing fuel delivery during cold start is the right behavior. Reducing fuel at start would make starting harder, no enrichment would hinder starting, and increasing fuel after warm-up isn’t addressing the cold-start condition.