Engine Controls - Basic Diagnostic Procedures: Other Volkswagen EuroVan T4 рестайлинг

Exhaust System Backpressure

A restricted exhaust system can be checked with a vacuum or pressure gauge. Remove heated oxygen sensor or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and operate engine at 2500 RPM. If exhaust system backpressure is greater than 3 psi, exhaust system or catalytic converter is plugged.

If a vacuum gauge is used, connect vacuum gauge hose to intake manifold vacuum port and start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for restriction.

FUEL PRESSURE

Basic diagnosis of fuel system should begin with determining fuel system pressure.

Fuel System Pressure Release (2.8L VR6, Engine Code AES)

Fuel system is pressurized! Wrap a cloth around the connection before loosening hose connections or opening a test connection. Carefully release pressure by pulling off the hose or by removing the plug.

Scheme 50

Scheme 51

1. Ensure ignition is off. Ensure battery voltage is at least 12 volts. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AES)»(ref-162789-S26523601172004061000000).
2. Remove plug (1) on fuel pressure regulator bracket. (Scheme 50) Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply test connection. Ensure shut-off valve is in closed position (90 degrees to direction of fuel flow). Fuel pressure gauge shut-off valve must remain in closed position.
3. Start engine and idle. Fuel pressure should be within specification. See «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table.
4. Continue to idle engine. Disconnect vacuum line from fuel pressure regulator. (Scheme 51) For specification, see «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table.
5. If fuel pressure is not as specified, check fuel pump volume. See «FUEL PUMP VOLUME CHECK»(ref-162789-S33652546932004061000000). If fuel pressure is as specified, go to next step.
6. Perform fuel system residual pressure test. Reinstall vacuum hose on fuel pressure regulator and continue to run engine at idle. Turn engine off.
7. Check residual fuel pressure after 10 minutes. See «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table. If residual fuel pressure drops below specification, check for fuel leaks and repair as necessary. Recheck residual fuel pressure. If residual fuel pressure is still not as specified, start and idle engine. After fuel pressure build up, turn off ignition. At the same time clamp off fuel return line (blue markings) on fuel pressure regulator bracket.
8. Observe residual fuel pressure drop again. If fuel pressure does NOT drop, check for leaking fuel injectors or fuel pressure regulator. If fuel pressure drops, check for leaking fuel lines between fuel rail and fuel tank. Repair as necessary. If fuel lines are okay, test for faulty fuel pump check valve. See «FUEL PUMP CHECK VALVE»(ref-162789-S06345422592004090200000).

Note. To test for leaking fuel injectors, see FUEL INJECTOR TESTS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING article.

FUEL PRESSURE SPECIFICATIONS (2.8L VR6)

Fuel System Pressure Release (2.8L VR6, Engine Code AXK)

Turn ignition off. Remove fuel pump fuse No. 18 to deactivate fuel pump. (Scheme 52) Place a clean shop rag around fuel line fitting/hose and slowly loosen fitting/hose. (Scheme 53)

Note. Fuse/relay panel is located behind cover on driver's side storage (under dash).

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Scheme 56

1. Ensure ignition is off. Ensure battery voltage is at least 12 volts. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AXK)»(ref-162789-S22068107742004061400000).
2. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply line/hose in engine compartment. (Scheme 53)and (Scheme 54). Open shut-off valve of fuel pressure gauge; lever points in the direction of flow. Reinstall fuel pump fuse No. 18. NOTE: Depress buttons on fuel hose connection to disconnect hose.
3. Start engine and idle. Fuel pressure should be within specification. See «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table. If fuel pressure is as specified, go to next step. If fuel pressure is NOT as specified, check fuel pump volume. See «FUEL PUMP VOLUME CHECK»(ref-162789-S33652546932004061000000).
4. Continue to idle engine. Disconnect vacuum line from fuel pressure regulator (Scheme 55) For specification, see «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table.
5. If fuel pressure is not as specified, check fuel pump volume. See «FUEL PUMP VOLUME CHECK»(ref-162789-S33652546932004061000000). If fuel volume is okay, go to next step.
6. Perform fuel system residual pressure test. Reinstall vacuum hose on fuel pressure regulator and continue to run engine at idle. Turn engine off.
7. Check residual fuel pressure after 10 minutes. See «FUEL PRESSURE SPECIFICATIONS (2.8L VR6)»(ref-162789-S10103918752004061000000) table.
8. If residual pressure drops below specification, restart engine and let it idle.
9. When fuel pressure has built up, turn off ignition. At the same time, close shut-off valve on Pressure Gauge (VAG 1318). Lever will be at 90 degrees to fuel flow. (Scheme 56) Check residual fuel pressure again.
10. If residual fuel pressure does not drop, test for faulty fuel pump check valve. See «FUEL PUMP CHECK VALVE»(ref-162789-S06345422592004090200000). If residual fuel pressure drops again, check pressure gauge for leaks. Check for leaking fuel lines and connections. If no leaks are found, turn off ignition. Check for leaking fuel injectors or fuel pressure regulator.

Note. To test for leaking fuel injectors, see FUEL INJECTOR TESTS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING article.

Scheme 57

Scheme 58

Scheme 59

Scheme 60

1. Ensure battery voltage is at least 11.5 volts. Ensure fuel pump fuse No. 18 is okay. (Scheme 52) Turn ignition off. Remove fuel filler cap.
2. Relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AES)»(ref-162789-S26523601172004061000000).
3. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply line/hose in engine compartment. Ensure shut-off lever is open (position A), and fuel hose is in a measuring container. (Scheme 57)
4. Remove fuel pump relay from relay panel. Connect Remote Control Switch (VAG 1348) between battery positive source and fuel pump terminal. (Scheme 58)
5. Activate fuel pump with remoter control switch and slowly close lever (A) until pressure is at 44 psi (3 bar). (Scheme 57) Once this pressure is reached, do NOT move lever any further. Empty measuring container.
6. Connect DVOM to battery terminals. Activate fuel pump for 30 seconds while collecting fuel in measuring container and measure battery voltage. Record fuel volume and battery voltage.
7. Compare quantity of fuel with specification. (Scheme 59) NOTE: Voltage shown in graph in (Scheme 59) is at fuel pump. Battery volage is about 2 volts more than that measured directly at fuel pump.
8. If minimum fuel pump volume is not as specified, check fuel lines for possible restrictions, kinks or blockages. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel filter. (Scheme 60)
9. Repeat fuel pump volume check. If minimum volume is now reached, replace fuel filter.
10. Repeat fuel pump volume check. If minimum volume is still not reached, remove fuel pump and check strainer for clogging. If strainer is okay, replace fuel pump. NOTE: It is not necessary to drop fuel tank to access fuel pump. Remove driver's seat. Lift carpeting above parking brake lever. Remove fuel pump assembly access plate. (Scheme 61)
11. If fuel pump volume is okay, but an intermittent fuel supply problem is suspected, check fuel pump amperage draw. See «FUEL PUMP AMPERAGE DRAW»(ref-162789-S33073430532004090200000).

Scheme 61

Scheme 62

1. Ensure ignition is off. Ensure battery voltage is at least 12 volts. Release fuel pressure. See «FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AXK)»(ref-162789-S22068107742004061400000). Remove fuel filler cap.
2. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply line/hose in engine compartment. (Scheme 62) Open shut-off valve of fuel pressure gauge; lever points in the direction of flow (A). Reinstall fuel pump fuse No. 18 (if removed).
3. Remove fuel pump relay from relay panel. Connect Remote Control Switch (VAG 1348) between battery positive source and fuel pump terminal. (Scheme 58)
4. Activate fuel pump with remoter control switch and slowly close lever (A) until pressure is at 44 psi (3 bar). (Scheme 57) Once this pressure is reached, do NOT move lever any further. Empty measuring container.
5. Connect DVOM to battery terminals. Activate fuel pump for 30 seconds while collecting fuel in measuring container and measure battery voltage. Record fuel volume and battery voltage.
6. Compare quantity of fuel with specification. see scheme 18 NOTE: Voltage shown in graph in see scheme 18 is at fuel pump. Battery volage is about 2 volts more than that measured directly at fuel pump.
7. If minimum fuel pump volume is not as specified, check fuel lines for possible restrictions, kinks or blockages. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel filter. (Scheme 60)
8. Repeat fuel pump volume check. If minimum volume is now reached, replace fuel filter.
9. Repeat fuel pump volume check. If minimum volume is still not reached, remove fuel pump and check strainer for clogging. If strainer is okay, replace fuel pump. NOTE: It is not necessary to drop fuel tank to access fuel pump. Remove driver's seat. Lift carpeting above parking brake lever. Remove fuel pump assembly access plate. (Scheme 61)
10. If fuel pump volume is okay, but an intermittent fuel supply problem is suspected, check fuel pump amperage draw. See «FUEL PUMP AMPERAGE DRAW»(ref-162789-S33073430532004090200000).

FUEL PUMP CHECK VALVE

Note. It is not necessary to drop fuel tank to access fuel pump. Remove driver's seat. Lift carpeting above parking brake lever. Remove fuel pump assembly access plate. (Scheme 61)

2.8L VR6 (Engine Code AES)

1. Ensure battery voltage is at least 11.5 volts. Ensure fuel pump fuse No. 18 is okay. (Scheme 52) Turn ignition off.
2. Relieve fuel system pressure. See «FUEL SYSTEM PRESSURE RELEASE (2.8L VR6, ENGINE CODE AES)»(ref-162789-S26523601172004061000000).
3. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply line/hose in engine compartment. Ensure shut-off lever is closed (at 90 degrees to fuel flow, position B), and fuel hose is in a measuring container. (Scheme 57)
4. Remove fuel pump relay from relay panel. Connect Remote Control Switch (VAG 1348) between battery positive source and fuel pump terminal. (Scheme 58)
5. Operate remote control at short intervals until a pressure of about 44 psi (3 bar) has built up. If pressure builds up too high, lower excess pressure by carefully opening tap.
6. Observe pressure drop. After 10 minutes, fuel pressure must not drop below 32 psi (2.2 bar). Check line connections for leaks and/or replace fuel pump if necessary.

2.8L VR6 (Engine Code AXK)

1. Ensure battery voltage is at least 11.5 volts. Ensure fuel pump fuse No. 18 is okay. (Scheme 52) Turn ignition off.
2. Relieve fuel system pressure. See «Fuel System Pressure Release (2.8L VR6, Engine Code AXK)»(ref-162789-S22068107742004061400000).
3. Connect Pressure Gauge (VAG 1318), or equivalent, at fuel supply line/hose in engine compartment. Ensure shut-off lever is closed (at 90 degrees to fuel flow, position B), and fuel hose is in a measuring container. (Scheme 62)
4. Remove fuel pump relay from relay panel. Connect Remote Control Switch (VAG 1348) between battery positive source and fuel pump terminal. (Scheme 58)
5. Operate remote control at short intervals until a pressure of about 44 psi (3 bar) has built up. If pressure builds up too high, lower excess pressure by carefully opening tap.
6. Observe pressure drop. After 10 minutes, fuel pressure must not drop below 36 psi (2.5 bar). Check line connections for leaks and/or replace fuel pump if necessary.

FUEL PUMP AMPERAGE DRAW

Note. It is not necessary to drop fuel tank to access fuel pump. Remove driver's seat. Lift carpeting above parking brake lever. Remove fuel pump assembly access plate. (Scheme 61)

2.8L VR6

1. Access fuel pump through access cover under driver's seat. Ensure all fuel lines are connected.
2. Connect DVOM Red/Yellow wire on fuel pump connector using current measuring adapter.
3. Start engine and let it idle. Maximum amperage draw should be 8 amps.
4. If amperage draw is too high, replace fuel pump.

IGNITION SYSTEMS

Ignition system faults will set a DTC. For repair information, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

IDLE SPEED & IGNITION TIMING

Idle speed or ignition timing faults will set a DTC. For repair information, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.