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 1318/12-

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-

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; checking → Rep. Gr.20. l  Ignition off.

Checking fuel pressure –  Remove rear seat bench → Rep. Gr.72. –  Unscrew cover for flange (right-side) -arrows-.

–  Carefully release electrical connector from flange -arrow- and unplug.

–  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 -4- to the body (earth) using a test lead from auxiliary measuring set -V.A.G 1594 C-. –  Move switch of remote control -V.A.G 1348/3 A- to front of engine compartment.

–  Slide cover panel above positive terminal to the right -arrow 1- and lift off cover panel -arrow 2-.

–  Release retaining clip -arrow- and open cover -2- above positive terminal. –  Connect crocodile clip to positive power supply (+) -3-.   Note Disregard -item 1-.

–  Pull off engine cover panel (rear) -arrows-.

–  Remove bolts -1-. –  Disengage retaining clip -2- and detach bracket for engine cover panel (rear).   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 -arrow- at fuel rail.

–  Connect pressure gauge -V.A.G 1318- with adapters -V.A.G 1318/11- and -V.A.G 1318/12- to fuel line. –  Fit test hose -arrow- onto pressure tester and hold end of hose into a container to catch escaping fuel. –  Open cut-off valve on pressure tester. Lever points in direction of flow. –  Bleed fuel system by pressing remote control briefly.

–  Close cut-off valve on pressure gauge. Lever is at right angle to direction of flow -arrow-. –  Press switch on remote control until pressure gauge shows no further increase in pressure. l  Specification: approx. 6 bar If specification is not obtained: –  Check fuel delivery rate of fuel pump → Rep. Gr.20. Checking 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 bar. If the residual pressure drops below 3 bar: t  Check union between pressure gauge and fuel line for leaks. t  Test pressure gauge for leaks. t  Check fuel lines and their connections for leaks. t  Renew fuel filter with integral fuel pressure regulator → Rep. Gr.20. t  Renew fuel pump → Rep. Gr.20. Assembly is carried out in the reverse order; note the following:   Note Before removing the pressure tester, release the fuel pressure by opening the cut-off valve. Hold a container under the connection. l  Tightening torque: refer to exploded view of high-pressure pump → Chapter.