Audi Workshop Service and Repair Manuals

Checking initial fuel pressure up to mechanical high-pressure pump   Note t  Control unit for electric fuel pump OK. t  Fuel pump OK. t  Fuel filter OK t  Battery voltage at least 11 Volt –  Switch on ignition.   Note The engine control unit is selected below using the VAS 5051 under the function “Read data block” and the display group 140.

–  Connect vehicle diagnostic, testing and information system -VAS 5051B- with diagnostic cable -VAS 5051/1-.

Display on tester: –  Press the “Vehicle self-diagnosis” key.

Display on tester: –  From list -1- select vehicle system “01 Engine electronics”.

Display on tester: 1 -  Selection of diagnostic functions: –  From list -1- select diagnostic function “08 - Read measured value block”.

Display on tester: –  Use keypad -2- to enter display group number 140 and confirm entry by pressing the Q key.

Display on tester: 1 -  Display group X 2 -  Display zone 1  -  Display zone 2  -  Display zone 3  -  Display zone 4 Observe the reading in display zone 3. The display shows the current (actual) pressure in the fuel rail. Display zone 2 shows the specified pressure (required pressure). The values for specified pressure and actual pressure should be equal.   Note When the ignition is switched off and on, the fuel pump control unit -J538- will activate the electric fuel pump for several seconds. The initial fuel pressure can only be measured during this time. –  Switch the ignition off and back on again (when a message appears, press repeat.) –  Measure the fuel pressure. t  Specification: approx. 6 bar (5 ... 7 bar) –  If reading does not match specification, check electric fuel pump → Rep. Gr.20.