Air injection - function - GF14.30-P-3012BK

ENGINE 113.967 in MODEL 219 

ENGINE 113.964 in MODEL 164.1 

ENGINE 113.971 in MODEL 251 

Shows model 219 

Fig 1: Air Injection Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The air injection heats up the catalytic converters more rapidly to its operating temperature and thus improves the emission levels in the warming-up phase.

The electric air pump (M33) is actuated through the air injection relay. The current consumption of the electric air pump (M33) is as much as 40 A.

The air injection relay and air pump switchover valve are actuated by the motor electronics control unit simultaneously for a maximum of 40 seconds following engine start if the following conditions are fulfilled:

• Coolant temperature -10°C and < 35°C
• Coolant temperature 0+7°C and < 35°C
• Engine speed < 2500 RPM.

Following actuation, air injection remains locked if it has run sufficiently long enough to warm up the catalytic convertors (maximum 40 seconds). A new enable of the air injection will only take place if the catalytic convertors cool down again due to a sufficiently long stoppage of the engine. For the purpose of diagnosis, air injection can also be enabled for a short time when the engine is warm.

If the electric air pump is actuated over the air pump relay then it sucks in injected air from the air cleaner and pushes it to the aspirator shutoff valves.

The air pump switchover valve is actuated parallel to the air pump.

Thus the vacuum passes from the intake manifold to the aspirator shutoff valve aneroid capsules.

The aspirator shutoff valves open and the air transported by the air pump is pressed through bore holes to the outlet ducts.

Check valves are integrated into the aspirator shutoff valves which prevent reverse current of hot exhaust gases into the aspirator shutoff valves and to the air pump.

The injected air reacts with the hot exhaust gases in the outlet port. An oxidation of carbon monoxides (CO) and hydrocarbon (HC) takes place and results in an additional increase in the exhaust temperature.

Air injection may be actuated deliberately using STAR DIAGNOSIS for a maximum of 2 minutes. Prior to the next actuation, it is essential to maintain a cooling time of 30 minutes, otherwise the air pump may be damaged.