Audi Workshop Service and Repair Manuals

Checking fuel pressure and residual pressure (up to high-pressure pump)

Special tools and workshop equipment required

t	Pressure tester -V.A.G 1318-

t	Adapter -V.A.G 1318/11-

t	Adapter -V.A.G 1318/17-1- from adapter set -V.A.G 1318/17-

t	Connector -V.A.G 1318/23-

t	Remote control -V.A.G 1348/3 A- with adapter cable -V.A.G 1348/3-3-

t	Auxiliary measuring set -V.A.G 1594 C- or -V.A.G 1594 A-

t	Fuel-resistant measuring container

Test conditions l  Battery voltage at least 12.5 V l  Fuel filter OK l  Fuel tank at least 1/4 full. l  Fuel pump control unit -J538- OK (check) l  Ignition off.

Test sequence –  Remove rear seat → General body repairs, interior; Rep. Gr.72. –  Unclip retaining tabs -arrows- for flange cover.

–  Unplug electrical connector -arrow- at flange.

–  Connect remote control -V.A.G 1348/3 A- with adapter cable -V.A.G 1348/3-3- to contact -1- using a test lead from auxiliary measuring set -V.A.G 1594 C-. –  Tape off 2nd connector contact of the adapter cable -V.A.G 1348/3-3- with insulating tape -arrow- to prevent short circuits. –  Connect contact -5- to the body (earth) using a test lead from auxiliary measuring set -V.A.G 1594 C-. –  Connect crocodile clip to positive (+) terminal of battery. –  Remove filler cap from fuel filler neck.   WARNING Fuel system is pressurised (low pressure). Wear safety goggles and protective clothing to avoid possible injury and skin contact. Before opening the fuel system, wrap a cloth around the connection. Then dissipate pressure by carefully detaching the connection.

–  Disconnect fuel supply pipe -3- by pulling release tab.   Note The fuel return pipe -2- and vacuum pipe -1- remain connected (if fitted).

–  Screw connector -V.A.G 1318/23- and adapter -V.A.G 1318/17-1- onto pressure gauge -V.A.G 1318-. –  Fit adapter -V.A.G 1318/17-1- onto the disconnected fuel supply pipe. –  Screw the adapter -V.A.G 1318/11- onto the pressure gauge -V.A.G 1318-. Attach test hose -arrow- and hold end of hose in measuring container. –  Open cut-off tap on pressure tester -V.A.G 1318-. Lever must point in direction of flow. –  Bleed fuel system by pressing remote control switch briefly.

–  Close cut-off tap on pressure tester -V.A.G 1318-. Lever is at right angle to direction of flow -arrow-. –  Press and hold remote control switch until pressure tester -V.A.G 1318- shows no further increase in pressure. l  Specification: approx. 6 bar (5 ... 7 bar). If specification is not obtained: –  Check delivery rate of fuel pump → Fuel supply system, petrol engines; Rep. Gr.20. Checking residual pressure –  Check for leaks and check residual pressure by watching drop in pressure on pressure tester -V.A.G 1318-. l  After 10 minutes pressure should still be at least 3.75 bar. If the residual pressure drops below 3.75 bar: t  Check union between pressure tester -V.A.G 1318- and fuel supply line for leaks. t  Check pressure tester -V.A.G 1318- for leaks. t  Check fuel lines and their connections for leaks. t  Renew fuel filter with integrated fuel pressure regulator → Fuel supply system, petrol engines; Rep. Gr.20. Then repeat the test. t  If fuel filter is OK, renew fuel pump → Fuel supply system, petrol engines; Rep. Gr.20. Assembly is carried out in the reverse order; note the following:

–  Switch off ignition.   Note Before removing the pressure tester, release the fuel pressure by opening the cut-off valve. Hold end of test hose in a container. –  Re-install fuel supply line (make sure that all parts are clean).