Air Injection: Description and Operation

GF14.30-P-3012M Air Injection, Function
ENGINE 275.950 in MODEL 215, 220
ENGINE 275.951 in MODEL 230 up to Model Year 8
ENGINE 275.953 in MODEL 216, 221 up to Model Year 8
ENGINE 275.954 in MODEL 230 up to Model Year 8
ENGINE 275.980 in MODEL 215, 220
ENGINE 275.981 in MODEL 230 up to Model Year 8
ENGINE 275.982 in MODEL 216, 221 up to Model Year 8
ENGINE 285.950 in MODEL 240
ENGINE 285.980 in MODEL 240





Shown on models 215, 220, 230, 240

126/1 Shutoff valve air injection, left cylinder bank
126/2 Shutoff valve air injection, right cylinder bank
128 Check valve (vacuum)

B11/4 Coolant temperature sensor
B28/7 Pressure sensor downstream of throttle valve actuator
B37 Accelerator pedal sensor
K17 Air injection relay (model 240)
K40/4kO Air pump replay (model 230)
K40/7kN Air pump replay (model 215, 220)
L5 Crankshaft position sensor
M16/6 Throttle valve actuator
M33 Electric air pump
N3/10 ME-SFI [ME] control unit
Y32 Air pump switchover valve
Y62 Fuel injection valves

a Vacuum
b Injected air
c Injected air to cylinder head

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

The electric air pump is actuated via the air pump relay or secondary air injection. The current consumption of the electric air pump is as much as 35 A.

The air injection relay and air pump switchover valve are actuated by the ME-SFI [ME] control unit simultaneously for a maximum of 90 s after the engine start if:

- Coolant temperature greater than 10°C and < 60°C
- Engine speed < 2500 rpm

After actuation the secondary air injection remains locked until the coolant temperature has risen to greater than 60°C and then drops again to below < 40°C.

The electric air pump sucks in air via a maintenance free filter and pushes in to the air shutoff valves.

The air pump switchover valve is supplied with vacuum from the intake manifold through a check valve. The air pump switchover valve, when actuated, switches the intake manifold pressure through to the air shutoff valve. The aspirator shutoff valves open and the air supplied by the air pump is forced through holes in the cylinder heads to the exhaust side.
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.

Integral check valves in the air shutoff valves prevent reverse current of exhaust gases to the electric air pump.