Volkswagen Workshop Service and Repair Manuals

Engine code AAZ =>Page 21-31

Engine code AFN

=> Repair group 23; Servicing diesel direct injection system; Checking charge air system

Special tools, testers and auxiliary items

• ◆ Turbocharger tester V.A.G 1397 A

Engine code 1Z, AHU

Check conditions

• ● No fault stored in fault memory

=> Repair group 01; Self-diagnosis; Interrogating fault memory

• ● Carry out final control diagnosis

=> Repair group 01; Self-diagnosis; final control diagnosis

• ● No leaks on intake and exhaust systems.
• ● Control pipe to charge pressure regulating valve is not blocked, loose or leaking.
• ● No faults in engine and fuel injection system, e.g. commencement of injection, injectors and compression pressure.

• ● Engine oil temperature min. 80 °C

Test sequence

• ‒ The charge pressure is measured under full load, whilst driving or on a rolling road. Test duration per measurement max. 10 seconds.
• ‒ → Pull off charge pressure control solenoid valve (N75) -1- connectors -2-.

• ‒ → Pull off connecting hose running between intake manifold and diesel direct injection system control unit (J248) and using T-piece connect in turbocharger tester V.A.G 1397 A.
• ‒ Select measuring range ll.

Notes:

• ◆ To operate turbocharger tester see operating instructions.
• ◆ The hoses must be connected so that there is no possibility of leaks.
• ◆ If boost pressure is measured whilst driving, it is necessary for safety reasons, for a second person to operate the turbocharger tester.
• ◆ Ensure that the pressure hose is not trapped between the bonnet and the body.

• ‒ Measure charge pressure at full throttle:
       On a rolling road:
       In 3rd gear or selector lever position 2 at
       3500...4000 rpm.
       Whilst driving:
       In 2nd gear or selector lever position 1
       at full throttle acceleration whilst observing
       rev counter.

Note:

The brake pedal must not be operated whilst taking measurements. The control unit thus reduces the fuel quantity which leads to incorrect measurements.

• ‒ Press the memory button "M" on turbocharger tester at 3500...4000 rpm and read off values.
       Specification: (Relative pressure)
       0.50...0.65 bar

If the charge pressure is not attained:

• ‒ Check charge pressure control valve pressure unit and renew if necessary.
• ‒ Repeat charge pressure check.

If the charge pressure has still not been attained:

• ‒ Replace turbocharger.

If the charge pressure is exceeded:

• ‒ Test charge pressure control solenoid valve (N75). (Through-flow in hose from turbocharger via valve to pressure unit when connector is pulled off).
• ‒ Check pressure unit for charge pressure regulating valve is securely mounted on turbocharger.
• ‒ Check charge pressure control valve pressure unit as well as the operating rod and renew if necessary.
• ‒ Check shaft mounting for charge pressure regulating valve in turbocharger for ease of movement.
  When corroded together, renew turbocharger.

Engine code AAZ

Turbocharger and wastegate constitute one unit. A defective turbocharger becomes an item for exchange, as repairs with workshop equipment are not possible.

Prerequisites for the perfect functioning of the turbocharger and attainment of prescribed boost pressure are:

• ● No leaks on intake and exhaust systems.
• ● Control pipe to charge pressure regulating valve is not blocked, loose or leaking.
• ● No faults in engine and fuel injection system, e.g. commencement of injection, maximum speed, injectors and compression pressure.

Test sequence

• ‒ The charge pressure is measured under full load, whilst driving or on a rolling road. Test duration per measurement max. 10 seconds.

• ‒ → Pull hose, running between intake manifold -1- and injection pump -2-, off at one end and using T-piece connect turbocharger tester in.

Notes:

• ◆ To operate turbocharger tester see operating instructions.
• ◆ If boost pressure is measured whilst driving, it is necessary for safety reasons, for a second person to operate the turbocharger tester.
• ◆ Ensure that the pressure hose is not trapped between the bonnet and the body.

• ‒ boost pressure measured at full throttle:
       On a rolling road:
       In 3rd gear or selector lever position 2 at 4000 rpm.
       Whilst driving:
       In 2nd gear or selector lever position 1 whilst simultaneously brak-          ing the vehicle to approx. 60 km/h.
       Specification: (Relative pressure) 0,60 ... 0,83 bar
• ‒ If the specifications are not achieved, renew turbocharger.
• ‒ If the boost pressure is too high and if the control pipe to wastegate is not blocked, loose or leaking, then also replace turbocharger as the boost pressure regulator is defective.