Audi Workshop Service and Repair Manuals

Procedure before opening high-pressure section of injection system t  The injection system consists of a high-pressure section (maximum approx. 110 bar) and a low-pressure section (approx. 6 bar). t  Before removing a component in the high-pressure section of the injection system, the fuel pressure in the high-pressure section must be reduced to a residual pressure of approx. 6 bar; follow the procedure outlined below. Special tools and workshop equipment required t  Vehicle diagnostic, testing and information system -VAS 5051B-

Procedure –  With ignition switched off, connect vehicle diagnostic, testing and information system -VAS 5051B- with diagnosis lead to diagnosis connection. –  Start the engine and run at idling speed.

Display on -VAS 5051B-: –  Select Vehicle self-diagnosis from the list -item 1-.

Display on -VAS 5051B-: –  From menu -1-, select vehicle system „Engine electronics“ and press → key to continue.

Display on -VAS 5051B-: –  From menu -1-, select function „Measured values“ and press → key to continue.

Display on -VAS 5051B-: –  Press keys 140 on keypad -1- to select „Display group 140“ and confirm entry by pressing Q key.

Display on -VAS 5051B-: –  Check display indicating fuel pressure in fuel rail in display zone -3-. l  With engine idling the figure displayed will be approx. 70 bar. The display shows the actual pressure in the fuel rail which is being generated by the high-pressure pump.

–  Detach cover from 9-position relay carrier / fuse holder on left side of dash panel. –  Remove fuse 18 in fuse holder B -SB18- for fuel system pressurisation pump -G6- on left side of dash panel.

Display on -VAS 5051B-: –  With engine still running, check display zone -3- for fuel pressure in fuel system: l  The fuel pressure will decrease very quickly because the mechanical high-pressure pump is no longer being supplied with fuel from the fuel tank by the electric fuel pump. –  Switch off ignition as soon as fuel pressure has dropped to just below 8 bar.   Note Fuel pressure must not fall below 6 bar, otherwise the engine will stall (this could damage the catalytic converter). The fuel rail is still filled with fuel, however it is no longer under high pressure.   WARNING There is a risk of injury: avoid skin contact with fuel. t  Wear safety goggles and protective clothing when opening the fuel system. t  Before opening the high-pressure section of the fuel system, place a clean cloth around the connection to catch escaping fuel. –  Disconnect a fuel line connection without delay.   Note The pressure will increase again due to the effect of residual heat if the high-pressure system is not opened immediately. Additional steps required –  Re-fit fuse 18 in fuse holder B -SB18-. –  With ignition switched off, connect vehicle diagnostic, testing and information system -VAS 5051B-. –  Start „Guided Functions“ mode. –  Generate readiness code in engine control unit → Vehicle diagnostic, testing and information system VAS 5051.