3304 & 3306 – Air Starting System

The air starting motor is used to turn the engine flywheel fast enough to get the engine running.

1. Starter control valve. 2. Oiler. 3. Relay valve. 4. Air starting motor.

The air starting motor is on the right side of the engine. Normally the air for the starting motor is from a storage tank which is filled by an air compressor installed on the left front of the engine. The air storage tank holds 10.5 cu. ft. (297 liter) of air at 250 psi (1720 kPa) when filled.

For engines which do not have heavy loads when starting, the regulator setting is approximately 100 psi (690 kPa). This setting gives a good relationship between cranking speeds fast enough for easy starting and the length of time the air starting motor can turn the engine before the air supply is gone.

If the engine has a heavy load which can not be disconnected during starting, the setting of the air pressure regulating valve needs to be higher in order to get high enough speed for easy starting.

The air consumption is directly related to speed, the air pressure is related to the effort necessary to turn the engine flywheel. The setting of the air pressure regulator can be up to 150 psi (1030 kPa) if necessary to get the correct cranking speed for a heavily loaded engine. With the correct setting, the air starting motor can turn the heavily loaded engine as fast and as long as it can turn a lightly loaded engine.

Other air supplies can be used if they have the correct pressure and volume. For good life of the air starting motor, the supply should be free of dirt and water. The maximum pressure for use in the air starting motor is 150 psi (1030 kPa). Higher pressures can cause safety problems. The 1L5011 Regulating and Pressure Reducing Valve Group has the correct characteristics for use with the air starting motor. Most other types of regulators do not have the correct characteristics. Do not use a different style of valve in its place.

5. Air inlet. 6. Rotor. 7. Vanes. 8. Pinion. 9. Gears. 10. Piston. 11. Pinion spring.

The air from the supply goes to relay valve (3). The starter control valve (1) is connected to the line before the relay valve (3). The flow of air is stopped by the relay valve (3) until the starter control valve (1) is activated. Then air from the starter control valve (1) goes to the piston (10) behind the pinion (8) for the starter. The air pressure on the piston (10) puts the spring (11) in compression and puts the pinion (8) in engagement with the flywheel gear. When the pinion is in engagement, air can go out through another line to the relay valve (3). The air activates the relay valve (3) which opens the supply line to the air starting motor.

The flow of air goes through the oiler (2) where it picks up lubrication oil for the air starting motor.

The air with lubrication oil goes into the air motor. The pressure of the air pushes against the vanes (7) in the rotor (6). This turns the rotor which is connected by gears (9) to the starter pinion (8) which turns the engine flywheel.

When the engine starts running the flywheel will start to turn faster than the starter pinion (8). The pinion (8) retracts under this condition. This prevents damage to the motor, pinion (8) or flywheel gear.

When the starter control valve (1) is released, the air pressure and flow to the piston (10) behind the starter pinion (8) is stopped, the pinion spring (11) retracts the pinion (8). The relay valve (3) stops the flow of air to the air starting motor.

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