If you try to start an engine that is already running, what will happen?

If you try to start an engine that is already running, what will happen?

• A. the engine will stall
• B. the battery will recharge
• C. no effect on the engine
• D. can cause significant starter damage

Answer: (D)

Engaging the starter while the engine is already turning is harmful because the starter is meant to crank a stopped engine. If you try to start it when it’s running, the starter gear (pinion) can collide with the moving flywheel, which can grind teeth, strip the gears, or burn out the starter by drawing excessive current. This can damage the starter and related components and isn’t something you want to risk. The engine will continue running, so it won’t stall because of a second attempt, and starting won’t magically recharge the battery—those aren’t the effects you’d expect. That’s why the potential for significant starter damage is the best answer.

Engaging the starter while the engine is already turning is harmful because the starter is meant to crank a stopped engine. If you try to start it when it’s running, the starter gear (pinion) can collide with the moving flywheel, which can grind teeth, strip the gears, or burn out the starter by drawing excessive current. This can damage the starter and related components and isn’t something you want to risk. The engine will continue running, so it won’t stall because of a second attempt, and starting won’t magically recharge the battery—those aren’t the effects you’d expect. That’s why the potential for significant starter damage is the best answer.