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| Remove the fuel return line (black or with black markings) -B- from the fuel supply unit. |
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| Connect -VAS 6550/1- pressure tester line to fuel return -B-. |
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| Guide the open end of the line into a suitable container. |
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| Connect vehicle diagnosis tester and perform the guided function „Checking electric fuel pump(s)“ or „Draining fuel system“ depending on software version. |
Note | The fuel pump is now activated. Actuation is limited to 30 s with guided function „Checking electric fuel pump(s)“. Repeat procedure until fuel tank is completely empty. |
| Fuel tank completely empty: |
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| Remove the fuel delivery unit and check the fuel tank for soiling and chippings. |
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| When required, clean the fuel tank and then install back in the fuel supply unit. |
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| Fill fuel tank with 5 litres of diesel and drain it again using guided function „Checking electric fuel pump(s)“ or „Draining fuel system“. |
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| Renew following high-pressure components: |
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| High-pressure accumulator (rail) including fuel pressure regulating valve -N276- and fuel pressure sender -G247- → Chapter |
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| Fuel return lines (overflow oil lines) → Item |
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