Engine Controls - System & Component Testing: Other Audi A4 B5 facelift

FUEL SYSTEM

FUEL PRESSURE RELEASE

Remove fuel pump relay. Start engine. Allow engine to run until it stalls. Turn ignition off. Disconnect negative battery cable. Slight pressure may remain in system. Before disconnecting any fuel system line, cover connector with a clean shop towel. Reinstall fuel pump relay.

Fuel System Pressure

1. Ensure fuel pump relay is okay. Ensure correct fuel filter is installed. Ensure battery voltage is at least 12 volts. Release fuel pressure. Ensure ignition is off.
2. Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. Disconnect and plug vacuum line from fuel pressure regulator. Following VAG 1551 scan tool manufacturer's instructions, energize fuel system.
3. Fuel pressure should be within specification. See appropriate FUEL PRESSURE SPECIFICATIONS table. If fuel pressure is within specification, perform «FUEL SYSTEM RESIDUAL PRESSURE»(ref-3057-S21911023682000041700000) test. If fuel pressure is not within specification, check fuel pressure regulator, fuel pump and fuel lines. Repair or replace as necessary.

Fuel System Residual Pressure

1. Tee fuel pressure gauge into fuel supply line. Start engine and let it idle. Turn engine off. See appropriate FUEL PRESSURE SPECIFICATIONS table.
2. If residual fuel pressure is minimum or more, residual fuel pressure is okay. If residual fuel pressure is less than minimum, check fuel lines for leaks and repair as necessary. Check fuel injectors for leaks. See «FUEL INJECTOR TEST»(ref-3057-S05672199772000041700000) . On 2.8L engine, check fuel pump check valve for malfunction. See «FUEL PUMP CHECK VALVE TEST»(ref-3057-S16494432712000041700000) .

FUEL PRESSURE SPECIFICATIONS (1.8L TURBO)

FUEL PRESSURE SPECIFICATIONS (2.8L)

2.8L

1. Connect Pressure Gauge (VAG 1318) between fuel supply and fuel return lines in engine compartment. Ensure pressure gauge test valve is in OPEN position.
2. Operate remote control switch for approximately 30 seconds. Move pressure gauge test valve to CLOSED position. Briefly operate remote control switch until maximum of 80 psi (5.5 bar) is indicated. Observe pressure drop on fuel pressure gauge.
3. After 10 minutes, maximum allowable pressure drop is 7 psi (.5 bar). If pressure drop is more than allowable maximum, ensure no fuel leaks are present in fuel lines. If no fuel leaks are present in fuel lines, fuel pump check valve is defective. Replace fuel pump.

A4 (1.8L Turbo) Fuel Pump Relay Function

1. Fuel pump relay is located in position No. 6 of relay panel located under left side of instrument panel. (Scheme 18) Remove fuel pump relay. Remove cover from end of left side of dashboard. Remove fuses No. 28, 29 and 34.
2. Connect VAG 1527B voltage tester between either terminal for fuse No. 28 and ground. Briefly operate starter motor. Fuel pump relay must audibly click and be felt energizing. Also, voltage tester should light up. If voltage tester does not light up, go to next step. If fuel pump relay does not operate, check and repair fuel pump relay power supply as necessary. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-3061) article.
3. Connect voltage tester to other terminal for fuse No. 28. Repeat step 2. If voltage tester still does not light up, repair wiring harness between fuse No. 28 and terminal No. 30 of fuel pump relay connector. (Scheme 18) See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-3061) article.

A4 (1.8L Turbo) Voltage Supply

1. Fuel pump relay is located in position No. 6 of relay panel located under left side of instrument panel. (Scheme 18) Remove fuel pump relay.
2. Turn ignition on. Connect a DVOM between fuel pump relay connector terminals No. 28 and 34. (Scheme 18) Note voltage reading. Connect DVOM between fuel pump relay connector terminals No. 32 and 34.
3. Voltage should be approximately battery voltage for each measurement. If voltage is not as specified, repair wiring harness as necessary. If voltage is as specified, voltage supply to fuel pump relay is okay.

A4 (1.8L Turbo) Fuel Pump Relay Signal

1. Fuel pump relay is located in position No. 6 of relay panel located under left side of instrument panel. (Scheme 18) Remove fuel pump relay.
2. Remove cover from end of left side of dashboard. Remove fuses No. 28, 29 and 34. Connect VAG 1527B voltage tester between fuel pump relay connector terminals No. 28 and 29. Voltage tester should dimly light. Briefly crank starter. Voltage tester should continue to dimly light. If voltage tester does not light as specified, go to next step. If voltage tester lights as specified, fuel pump relay signal is okay. Test is complete.
3. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. Connect VAG 1598/22 test box to PCM wiring harness.
4. Connect DVOM to test box socket 4 and fuel pump relay connector terminal No. 29. Resistance should be a maximum of one ohm. If resistance is within specification, go to next step. If resistance is not within specification, repair wiring harness as necessary. See WIRING DIAGRAMS article. Test is complete.
5. If wiring is okay, but voltage tester does not light, replace Powertrain Control Module (PCM). If wiring is okay and fuel pump relay signal is okay, replace fuel pump relay.

A4 (2.8L)

1. Fuel pump relay is located in position No. 6 of central electrical panel located under left side of instrument panel. (Scheme 18) Remove cover from end of left side of dashboard. Remove fuses No. 28, 29 and 34.
2. Connect VAG 1527B voltage tester between either terminal for fuse No. 28 and ground. Briefly operate starter motor. Fuel pump relay must audibly click and be felt energizing. Also, voltage tester should light up. If fuel pump relay does not operate, go to step 9. If voltage tester does not light up, go to next step.
3. Connect voltage tester to other terminal for fuse No. 28. Repeat step 2. If voltage tester still does not light up, repair wiring harness between fuse No. 28 and terminal No. 30 of fuel pump relay connector. (Scheme 18) Go to next step.
4. Connect VAG 1527B voltage tester between one terminal for fuse No. 29 and ground. Using VAG 1551 scan tool, trigger fuel pump relay. Voltage tester should light up. If voltage tester lights up, go to step 6. If voltage tester does not light up, go to next step.
5. Connect voltage tester between other terminal for fuse No. 29 and ground. Using VAG 1551 scan tool, trigger fuel pump relay. Voltage tester should light up. If voltage tester lights up, go to next step. If voltage tester still does not light up, repair wiring harness between fuse No. 29 and terminal No. 30 of fuel pump relay connector. (Scheme 18) Go to next step.
6. Connect VAG 1527B voltage tester between one terminal for fuse No. 34 and ground. Using VAG 1551 scan tool, trigger fuel pump relay. Voltage tester should light up. If voltage tester lights up, go to step 8. If voltage tester does not light up, go to next step.
7. Connect voltage tester between other terminal for fuse No. 34 and ground. Using VAG 1551 scan tool, trigger fuel pump relay. Voltage tester should light up. If voltage tester lights up, go to next step. If voltage tester still does not light up, repair wiring harness between fuse No. 34 and terminal No. 31 of fuel pump relay connector. (Scheme 18) Go to next step.
8. Remove fuel pump relay from vehicle. Turn ignition on. Using a DVOM, check voltage between fuel pump relay connector terminals No. 28 and 34, then terminals No. 32 and 34. (Scheme 18) Voltage should be approximately battery voltage. If voltage is not to specification, repair wiring harness as necessary. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-3061) article. Test is complete. NOTE: During next step, if voltage tester is left connected for more than one second to relay terminals without operating starter, voltage tester will dimly light (from low current draw).
9. With fuel pump relay removed from vehicle, connect VAG 1527B voltage tester between fuel pump relay connector terminals No. 28 and 29. (Scheme 18) Turn ignition on. Voltage tester should light for approximately one second, then go out. When starter motor is operated, voltage tester should light. If voltage tester operates as specified, replace faulty fuel pump relay. If voltage tester does not operate as specified, go to next step.
10. Turn ignition off. Disconnect Powertrain Control Module (PCM) connectors. PCM is located in left rear corner of engine compartment inside electrical box. Connect VAG 1598/22 test box to PCM wiring harness. Terminal assignments of test box are identical to PCM connectors "A", "B", "C", "D" and "E".
11. Using a DVOM, check resistance between fuel pump relay connector terminal No. 29 and test box socket A5. Maximum resistance is one ohm. If resistance is within specification, replace faulty Powertrain Control Module (PCM). See «SELF-DIAGNOSTICS - INTRODUCTION»(ref-3050) article. If resistance is not within specification, repair open circuit as necessary. See appropriate wiring diagram in «WIRING DIAGRAMS»(ref-3061) article.

Scheme 18