Flush fuel system

AR47.60-P-0024RFW

Flush fuel system

06.12.2018

Engine

780 in model 253.992/993

MV

Manual valve

Hydrogen discharge area shown as an example

1

Fuel cell cover

2

Filler neck

 Danger

Risk of explosion caused by escaping hydrogen or overheating of the fuel tanks when working on the hydrogen system. Risk of frostbite to body parts caused by escaping gas and by touching component parts carrying gas when emptying fuel tanks. Risk of asphyxiation caused by inhalation of air diluted by hydrogen. Risk of burn injuries by coming into contact with an invisible pale blue hydrogen flame.

AS00.00-Z-0030-01B

Topical note

Notes on fuel cell system

AH00.00-P-0022-01RFW

Notes on safety-relevant components

AH00.00-Z-0019-01A

Flush fuel system

1

Check whether the manual valve (MV) of the fuel tank to be flushed is open.

 The manual valves (MV) can be reached without lifting the vehicle.
The manual valves (MV) have a hexagon head with a wrench size of 7 mm.

If the manual valve (MV) of the fuel tank to be flushed is not open,



slowly open the manual valve (MV) completely and then turn it back a  revolution.

2

Park vehicle in the open air in the hydrogen discharge area, and secure it against unauthorized access and mark it.

 Comply with the safety clearance of  > 5 m from buildings.
The escaping hydrogen must not accumulate under roofs, detachable parts, etc.

 Start rinsing the fuel system promptly.
The temperature of the fuel tanks must be between 5 °C and 35 °C.
Suitable temperature measuring instruments are, e.g. commercially available laser temperature measuring instruments or infrared thermometers.

3

Deactivate the vehicle standby mode with the diagnostic system in the powertrain control unit (N127).



AD00.00-P-2000-04B

 To do this, select the following menu item:
Powertrain control unit (N127) 
Actuations 
Status of the start approval for the powertrain control unit component (N127).

4

Start the rinsing process with diagnostic system.



AD00.00-P-2000-04B


It is absolutely essential to perform the work procedures described below.
Otherwise, the fuel cell stack will be damaged.

 To do this, select the following menu item:
Fuel tank control unit (N3/19) 
Actuations 
Flushing fuel tank 1 or 2 with hydrogen.

5

Attach the drain fitting.



000 588 10 90 00 Evacuation hose

WS06.00-P-0025B

AR06.00-P-0001-01RFW

 Connector

*253589009100

 New passenger car wiring harness repair kit

*220589049900

 Unlocker with ejector MLK 1.2_plug

*220589019925

 Wiring harness repair kit, basic

*000589139900

6

Lower the engine hood and position it carefully in place.

 Do not damage the discharge hose.
The hydrogen sensor 3 (B72/11) in the engine hood monitors hydrogen leaks and interrupts the routine if a leak occurs.

7

Slowly fill the tank with hydrogen, gradually increasing the pressure until 100 bar has been reached.



000 588 12 82 00 Filling unit

WS06.00-P-0029B



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B


It is necessary for the tank temperature to be in the range of 5 to 35 °C before the filling starts.
Otherwise, the fuel tank will be damaged.


While filling the tank, monitor the tank temperature with the diagnostic system.
Do not overshoot the specified value of 85 °C.

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

 To do this, select the following menu item:
Fuel system control unit (N3/19) 
Actuations 
Flushing fuel tank 1 or 2 with hydrogen.

If the tank temperature is close to 85 °C,



Stop filling the tank until the tank temperature has fallen to the right level.

8

Relieve pressure in the filling nozzle and detach filling nozzle.



000 588 12 82 00 Filling unit

WS06.00-P-0029B

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

9

Seal filler neck (2) with the suitable dust cap for the vehicle.

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

10

Empty the fuel tanks, including line system with the diagnostic system, to 24 bar hydrogen­nitrogen mixture.



AD00.00-P-2000-04B

 To do this, select the following menu item:
Fuel tank control unit (N3/19) 
Actuations 
Flushing fuel tank 1 or 2 with hydrogen.

11

Slowly fill the tank with hydrogen again, gradually increasing the pressure until 100 bar has been reached.



000 588 12 82 00 Filling unit

WS06.00-P-0029B



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B


While filling the tank, monitor the tank temperature with the diagnostic system.
Do not overshoot the specified value of 85 °C.

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

 To do this, select the following menu item:
Fuel system control unit (N3/19) 
Actuations 
Flushing fuel tank 1 or 2 with hydrogen.

If the tank temperature is close to 85 °C,



Stop filling the tank until the tank temperature has fallen to the right level.

12

Relieve pressure in the filling nozzle and detach filling nozzle.



000 588 12 82 00 Filling unit

WS06.00-P-0029B

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

13

Seal filler neck (2) with the suitable dust cap for the vehicle.

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

14

Empty the fuel tanks, including line system with the diagnostic system, to 24 bar hydrogen­nitrogen mixture.



AD00.00-P-2000-04B

 To do this, select the following menu item:
Fuel tank control unit (N3/19) 
Actuations 
Flushing fuel tank 1 or 2 with hydrogen.

15

Remove the drain fitting.



000 588 10 90 00 Evacuation hose

WS06.00-P-0025B

AR06.00-P-0001-01RFW

 Stop plug to pressure regulating valve holder

*BA47.60-P-1032-01B

 Connector

*253589009100

 Wiring harness repair kit, basic

*000589139900

 New passenger car wiring harness repair kit

*220589049900

 Unlocker with ejector MLK 1.2_plug

*220589019925

16

Activate the vehicle standby mode with the diagnostic system in the powertrain control unit (N127).



AD00.00-P-2000-04B

 To do this, select the following menu item:
Powertrain control unit (N127) 
Actuations 
Status of the start approval for the powertrain control unit component (N127).

17

Lower the engine hood and position it carefully in place.

 The hydrogen sensor 3 (B72/11) in the engine hood monitors hydrogen leaks and interrupts the routine if a leak occurs.

18

Fill the medium pressure line system with 9 to 14 bar hydrogen via the diagnostic system.



AD00.00-P-2000-04B

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Actuations 
leak test of the system pressure.

 The hydrogen in the high-pressure line system is sufficient for filling.

19

Perform a leak test on the stop plug (arrow C).



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

 Use safety glasses and protective gloves.

 Specified value at the stop plug (arrow C): under 100 ppm with a measurement duration of 10 to 30 s.

If the specified value is exceeded:



Abort leak test and remove the leakage.

20

Slowly open the manual valve (MV) of the unrinsed fuel tank completely and then turn it back a  revolution.

If a fuel tank has been intertized or replaced.

 Commercially available devices/tools explosion-proof flashlight, comparable with AccuLux flashlight MHL 5 EX of the company Witte + Sutor GmbH.

21

Charge the high-voltage battery module (A100) to a charge level of 50 to 80 %, then remove the charging cable.

AR47.70-P-0009RFW

22

Fill the vehicle to 700 bar at a hydrogen filling station.

 The trip to and from the destination is powered by the electric battery.
The range is approx. 50 km.
If necessary, transport the vehicle on a passenger car transport trailer or a passenger car van.

23

Set the parameter for the inert gas concentration to 3,400 ppm.



AD00.00-P-2000-04B


It is absolutely essential to perform the work procedure described.
Otherwise, the fuel cell stack will be damaged.

 To do this, select the following menu item:
Fuel tank control unit (N3/19) 
Adaptations 
Teach-in processes 
Parameters of the fuel tank control unit (N3/19).

24

Perform a diagnosis-based activation of the fuel cell in the powertrain control unit (N127).



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B

 To do this, select the following menu item:
Powertrain control unit (N127) 
Actuations 
Status of the start approval for the fuel cell system component.

25

Start fuel cell system, let it run at a standstill for at least 5 min and read the fault messages in the instrument cluster.

AR06.00-P-0002-01RFW

If a fault message appears in the instrument cluster,



switch off fuel cell system and eliminate the fault.

26

Perform a brief diagnosis test.



AD00.00-P-2000-04B

27

Drive into the workshop.

28

Perform the "Special service, recurring check of gas system".



AP00.20-P-1310E

29

Install underfloor paneling.

AR61.30-P-1001RFW

30

Install fuel cell cover (1).

31

Place all filled-out logs in the order folder and store it in an appropriate location.

 Tank system

Number

Designation

Engine 780 in model 253.992/993
with code ME02 (Fuel cell)

BA47.60-P-1032-01B

Stop plug to pressure regulating valve holder

Nm

40