Component description for electric air pump

P14.30-2075-11

View of engine from front right

M33 Electric air pump

Location

The electric air pump is located at the front right, above the alternator (G2).

Task

The electric air pump blows fresh air into the cylinder head exhaust ports (for air injection).

Air injection allows afterburning in the exhaust ducts or in the firewall catalytic converters which brings the firewall catalytic converters more quickly up to operating temperature.

Design

The electrical air pump is an electric vane pump.

Function

When air injection is enabled, the electric air pump is actuated through the air pump relay (K40/4kO) for up to 90 s, at the same time as the air pump switchover valve (Y32).

The electric air pump draws the injected air out of the right air filter housing and delivers it via two pressure fittings through the air shutoff valves to the outlet ducts.

Following actuation, air injection remains locked. Air injection is only enabled again if the coolant temperature rises above 60°C and then falls below 40°C.

The electrical air pump also has sufficient time to cool down again.

 Diagnosis

Air injection can be released for diagnosis using DAS for a max. of 2 minutes (for a warm engine even shorter).

Prior to the next actuation, it is essential to maintain a cooling time of 30 minutes, otherwise the electric air pump may be damaged (overheated).

P07.61-2870-01

View of engine compartment from rear right

K40/4 Passenger-side fuse and relay module

K40/4f43 Fuse 43 (circuit 87 M1)

K40/4f44 Fuse 44 (circuit 87 M2)

K40/4kK Motor electronics/chassis relay

K40/4kL Starter relay

K40/4kM Terminal relay 30z (for AMG)

K40/4kO Air pump relay