In order to limit the shuddering of the engine whilst it is switching off, a throttle casing has been introduced downstream of the air chamber which has the task of closing the flow of air to the cylinders.The throttle remains open in all other operating conditions.
1 - Vacuum reservoir2 - Solenoid3 - Throttle casing control actuator4 - Throttle body5 - Injection control unit
Operation
When the engine is off, the throttle is open because no vacuum is present.When the engine is running, the throttle is open because the deactivated solenoid valve closes off the flow of the vacuum to the throttle casing pneumatic actuator.A vacuum builds up during engine operation.When the engine is turned off (the key is turned OFF), the injection control unit keeps the actuator supply relay supplied 4 or 5 seconds longer and simultaneously earths the solenoid valve. The valve then opens to send a vacuum to the pneumatic actuator which closes the throttle to cut off the air flow to the cylinders.
