🔍 Key Concepts

• Follow the pinion engaging line from the air supply through the solenoid valve and see which component it reaches first. • Notice which motor’s pinion is shown in the engaged vs retracted position in the illustration. • Understand that energizing the solenoid opens the path for air to move an actuator before the main cranking air flows to spin the motors.

💭 Think About

• When the start button is pressed, what does opening the solenoid air valve allow compressed air to do along the pinion engaging line? • Looking at the check valve location, which motor can receive the first movement/force to change its pinion position? • Would a starting system normally try to mesh a pinion with the flywheel before or after applying high‑volume cranking air to spin the engine? Apply that logic here.

✅ Before You Answer

• Verify which motor (upper or lower) is directly connected to the pinion engaging line coming from the solenoid air valve. • Confirm the function of the check valve—does it allow air to travel from the solenoid toward the motor actuator or back the other way? • Make sure your choice reflects the very first mechanical consequence: a change in pinion engagement, not yet the spinning of the engine.