Location
Shown on MODEL 963 |
1 | Pump module |
2 | Exhaust aftertreatment unit |
16 | AdBlue®tank |
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The pump module (1) which contains the SCR control unit (A58) and SCR delivery pump (M25) is fastened to a bracket on the inside of the right longitudinal frame member behind the EATU (2).
Task
The pump module (1) suck in AdBlue® from the AdBlue® tank (16), filters it and pumps it to the AdBlue® metering device (A67). The SCR control unit (A58) calculates the injection period and the injection quantity.
Structure
3 | Electronics housing |
4 | Connecting body |
5 | Filter housing |
6 | Electrical connection (communication to AdBlue® metering device) |
7 | Electrical connection (communication to exhaust aftertreatment (ACM) control unit) |
8 | AdBlue®inlet |
9 | Intake filter (mesh size 190 m) |
10 | AdBlue®outlet |
11 | Vent valves |
12 | Coolant inlet |
13 | Coolant outlet |
14 | Pressure limiting valve |
15 | Main filter (mesh size 20–30 μm) |
A58 | SCR control unit |
M25 | SCR delivery pump |
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Function
8 | AdBlue®inlet |
9 | Intake filter |
10 | AdBlue®outlet |
12 | Coolant inlet |
13 | Coolant outlet |
14 | Pressure limiting valve |
15 | Main filter |
M25 | SCR delivery pump |
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After the engine starts, the exhaust aftertreatment (ACM) control unit (A60) sends a message to the pump module (1) or, more accurately, the SCR control unit (A58) integrated into it. This switches the SCR delivery pump (M25) on so that AdBlue® is sucked in from the AdBlue® container and pumped at an operating pressure of approx. 10 bar towards the AdBlue® metering device (A67). Since the AdBlue®metering device (A67) is cooled by circulation through circulating AdBlue®, AdBlue® is pumped continuously, irrespective of whether injection is necessary or not. The AdBlue® that is not required or not injected flows back through the return line to the AdBlue® container.
Heating
A duct inside the connecting body (4) enables the pump module (1) to have engine coolant flow through it for heating or defrosting. The coolant inflow is regulated by an engine mounted solenoid valve as a function of the temperature by the engine management (MCM) control unit (A4).
Run-on
To avoid any damage through overheating on the AdBlue® metering device (A67), the pump module (1) continues to pump AdBlue® for some time after the engine stops so that the cooling can be maintained for a longer period.