Perform fuel cell leak test

AR06.00-P-0004RFW

Perform fuel cell leak test

07.11.2018

Engine

780 in model 253.992/993

1

Fuel cell cover

2

Filler neck

Pfeil A

Upper test point

Shown in removed condition

Pfeil B

Lower test point

MV

Manual valves

 Danger

Risk of suffocation due to inhalation of inert gases. Risk of injury when working on pressurized parts.

Wear safety glasses and protective gloves. Work in well-ventilated rooms only.

AS00.00-Z-0034-01RFW

 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



Check

1

Remove fuel cell cover (1).

2

Release pressure in fuel cell system with vehicle diagnosis system.

AR06.00-P-1001RFW

3

Remove transmission tunnel underfloor paneling and underfloor paneling in center right.

AR61.30-P-1001RFW

4

Perform a visual inspection of the fuel cell system.

 Check correct installation of the components of the fuel cell system after it has been installed.

5

Remove dust cap from the filler neck (2).

6

Fill the high-pressure line system with 20 to 50 bar forming gas via the filler neck (2).



000 588 21 21 00 Leak tester

WS47.00-P-0045B



Connect STAR DIAGNOSIS and read out fault memory

AD00.00-P-2000-04B

Pressurize fuel system

AR47.60-P-0017-01RFW

 The manual valves (MV) of both fuel tanks must have been sealed.

 Use commercially available forming gas bottle bundles.

 Do not remove the filling nozzle from the filler neck (2).

7

Perform a diagnosis-based fuel cell leak test.



AD00.00-P-2000-04B

 To do this, select the following menu item:
Fuel cell control unit (N116/2) 
Fuel cell stack (FCU) 
Actuations 
leak test of the "fuel cell stack" components

8

Perform a leak test on the upper test points (arrows A).



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 specified value at all test points (arrows A):  under 20 ppm with a measurement duration of 10 to 30 s.

If the specified value is exceeded:



Abort leak test and remove the leakage.

9

Raise the vehicle approx. 50 cm on a vehicle lift.

 Pay attention to the hose of the filling nozzle.

10

Perform a leak test on the lower test points (arrows B).



000 588 03 21 00 Gas detector

WS47.00-P-0019B

 Use safety glasses and protective gloves.

 Specified value at all test points (arrows B):  under 20 ppm with a measurement duration of 10 to 30 s.

If the specified value is exceeded:



Abort leak test and remove the leakage.

11

Release pressure in fuel cell system with vehicle diagnosis system.

AR06.00-P-1001RFW

12

Slowly open the manual valves (MV) of both fuel tanks completely and then turn it back a  revolution.

13

Briefly fill the high-pressure line systems with   50 bar hydrogen via the filler neck (2).



000 588 12 82 00 Filling unit

WS06.00-P-0029B


It is absolutely essential to perform the brief filling of the high-pressure line system.
Otherwise, it will not be possible to start the fuel cell aggregate in the line system due to the pressure differences.

14

Attach the dust cap to the filler neck (2) and close the tank flap.

15

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.

16

Perform a brief diagnosis test.



AD00.00-P-2000-04B

17

Attach transmission tunnel underfloor paneling and underfloor paneling in center right.

AR61.30-P-1001RFW

18

Install fuel cell cover (1).