Air Injection Pump: Description and Operation

GF14.30-P-2000MAR Component Description For The Electric Air Pump
ENGINE 156.981 in MODEL 230.470 as of Model Year 09 /Modification Year 08 model refinement package





View from left front (bumper detached)

M33 Electric air pump

Location
The electric air pump is located at the bottom left behind the front bumper.

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 40 s, at the same time as the air pump switchover valve (Y32).

The electric air pump then draws injected air through the air filter housing and delivers it through two pressure fittings and the air shutoff valves to the exhaust ports.

Following actuation, air injection remains locked. Renewed enable of air injection will only take place if the firewall catalytic convertors cool down again due to a sufficiently long stoppage time of the engine.

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).





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 Circuit 30z relay
K40/4kO Air pump relay