Audi Workshop Service and Repair Manuals

Checking system pressure, fuel pressure regulator and residual pressure   Note The fuel pressure regulator is integrated in the fuel filter and cannot be renewed on its own. Special tools and workshop equipment required

t  Hose clamps for hoses up to 25 mm Ø -3094-

t  K-Jetronic tester -V.A.G 1318- with adapters -V.A.G 1318/11-, -V.A.G 1318/17- and -V.A.G 1318/23- Test conditions l  Fuel pump relay OK. l  Fuel pump OK; checking → Rep. Gr.20. l  Fuel filter OK l  Battery voltage at least 12.5 V

Test sequence Measuring fuel pressure: –  Remove cover from fuse holder in dash panel (left-side) and pull out fuse SC27.   WARNING The fuel system is pressurised. Before opening the system place a clean cloth around the connection. Then release pressure by carefully loosening the connection.

–  Disconnect fuel supply pipe -2- at right rear of engine compartment by pulling release tab.   Note Disregard -item 1-.

–  Disconnect fuel supply pipe -arrow- at fuel rail.

–  Fit a fuel-resistant auxiliary hose -1- to fuel rail.   Note Use hose clips -arrows- to secure the auxiliary hose. –  Connect the K-Jetronic tester -V.A.G 1318- with adapters -V.A.G 1318/11-, -V.A.G 1318/17- and -V.A.G 1318/23-. –  Open cut-off valve on pressure tester. l  Lever points in direction of flow. –  Start the engine and run at idling speed. –  Measure the fuel pressure. l  Specification: approx. 4.0 bar –  Switch off ignition. If specification is not obtained: –  Check fuel pump delivery rate → Rep. Gr.20. Checking leakage and residual pressure: –  Check leak-tightness and residual pressure by watching the drop in pressure on the pressure gauge. l  After 10 minutes pressure should still be at least 3.0 bar. If the residual pressure drops below 3.0 bar: –  Start the engine and run at idling speed.

–  Allow pressure to build up, then switch off ignition. At the same time close cut-off valve of K-Jetronic tester -V.A.G 1318-. l  Lever is at right angle to direction of flow -arrow-. –  Observe pressure drop on pressure gauge. If the pressure drops again: –  Check pipe connections, O-rings on fuel rail and injectors for leaks. –  Check pressure gauge for leaks. If the pressure now does not drop: –  Open cut-off valve on pressure gauge (lever points in direction of flow). –  Remove rear seat bench → Rep. Gr.72.

–  Unclip the retaining tabs -arrows- for the flange cover (right-side).

–  Disconnect fuel return pipe -arrow- by pressing release tab.

–  Connect adapter hose -1318/17-1- to fuel return pipe. –  Clamp off adapter hose using hose clamp -3094-.   Note Do not attach hose clamp -3094- directly to fuel pipe - Danger of damage. –  Cover the return pipe connection with a cloth. –  Start the engine and briefly run at idling speed. –  Allow pressure to build up, then switch off ignition. –  Observe pressure drop on pressure gauge. If pressure does not drop, non-return valve of fuel pump is defective. –  Renew fuel pump → Rep. Gr.20. If the pressure drops again: –  Renew fuel filter with integral fuel pressure regulator → Rep. Gr.20.   Note Before removing the pressure tester, release the fuel pressure by opening the cut-off valve. Hold a container under the connection. –  Assembly is carried out in the reverse order; note the following: –  Re-insert fuse SC27 in fuse holder in dash panel (left-side). –  Install rear seat bench → Rep. Gr.72.