5 Series E60 520d (N47) SAL
Connection to atmosphere via
filter
2
Connection to intake manifold
vacuum
9
Open/closed valve (mechanical)
3
Spring
10
Intake valve
4
Connection to activated charcoal
filter
11
Pressure valve
5
Reed contact
12
Solenoid valve coil
6
Upper pump chamber
13
Electrical connections
7
Diaphragm
When the diaphragm (7, Fig. 2) is pulled up, a suction or pump effect is created under the
diaphragm. Suction/pressure valves allow the oscillations of the diaphragm to create a
pressure of approx. 25 hPa in the tank vent system, through the activated charcoal filter to
the fuel filler cap. The oscillations of the diaphragm, i.e. the frequency, is measured by the
reed contact (5, Fig. 2). The principle of pressure leakage diagnosis is based on a
measurement of the repumping frequency needed by the leak diagnosis pump:
•
Repumping frequency greater than nominal value: System leaking
•
Repumping frequency less than nominal value: System not leaking
2nd leakage check in OBD II (on-board diagnosis) with fuel tank leak diagnosis module
(DMTL)
This test procedure is able to detect leaks as small as > 0.5 mm in the fuel supply system.
It thus constitutes a significant improvement in terms of protecting the environment.
Start criterion
Start condition
Engine
OFF
Last engine standstill
> 5 h
Duration of current journey
> 10 min
Fuel level
> 15 % and < 85 %
Ambient temperature
> 4
°
C and < 35
°
C
Altitude above mean sea level
< 2500 m
Battery voltage
> 11.0 V and < 14.5 V
Table 2: Start conditions for diagnosis
2.1 Function description of fuel tank leak diagnosis module check
Once all start conditions listed in Table 2 are satisfied, the DMTL will automatically start a
tank leak measurement (OBD diagnosis).
The actual tank leak measurement comprises two phases: reference leak measurement
and tank leak measurement.
2.1.1 Reference leak measurement
During the reference leak measurement, the vane pump blows air through the so-called
reference leak (
∅
0.5 mm).
The power intake of the pump is measured and serves as the reference current during
subsequent leak diagnosis. The strength of this pump current is approx. 20 mA to 30 mA.
This initial procedure takes place within the DMTL only and no other parts are affected.
SI Diagnosis of fuel tank systems with fuel tank leak diagnosis module (DMTL) All U
BMW AG - TIS
23.01.2013 15:32
Issue status (12/2007) Valid only until next DVD is issued
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