Air Injection Pump: Description and Operation

2665 - Secondary Air Injection

Secondary Air Injection Pump







DIAGNOSIS: The secondary air system's functions are monitored by the oxygen sensor control. The secondary air injection pump is monitored by the DME.

Secondary air injection is activated by the Motronic control module. The air supplied by the secondary air injection opens the check valve through excess pressure, the air is then blown through the lines to behind the exhaust valves of the respective cylinder heads. The injection of secondary air leads to a reduction of the CO and HC pollutants that are created by operating with Lambda < 1, when starting out with an cold engine.

Additionally, the catalytic converters achieve their activation temperature of approx. 660 °F. (350 °C) more rapidly due to the waste heat created during the after burning. Activation conditions are achieved during the first cold start process if the coolant temperature is between 14 °F. (-10 °C) and + 108 °F. (42 °C). When running close to idle speed, secondary air injection is active for approx. 60 seconds, for a partial load up to 80 seconds. If during secondary air injection an intake air mass of approx. 332 kg/h is exceeded, the secondary air injection is deactivated.

Internal Design of Secondary Air Injection Pump