With the engine off
Check with your hand whether the actuator rod for adjusting the position of the guide vanes is jammed. If the stem is stuck, replace the turbocharger. Visually check the condition of the turbine and compressor (see illustrations for «Checking the turbocharger rotor»).
If one of the two wheels is damaged, also replace the piping coming from the damaged wheel.
If the stem is not jammed
At idle, with the boost pressure control solenoid valve controlled with SCR = 85%, disconnect the solenoid valve wire connector, observing that the guide vane air drive stem moves.
If the air actuator stem moves from stop to stop, the boost pressure regulator control circuit is working properly.
If the stem does not move
Check the condition of the boost pressure control solenoid valve connector (there are no signs of oxidation, bent pins, etc.). Check the resistance of the boost pressure control solenoid between tracks 1 and 2. It should be within:
- 15.4 Ohm±0.7 Ohm at + 20°C for Pierburg solenoid valve;
- 16.5 ohm±1.6 ohm at +25°C, for Bitron solenoid valve.
Solenoid valve defective
Replace the boost pressure control solenoid valve.
Solenoid valve OK
Check for open and short to +12 V and to «mass» wires in the circuit between track L2 of connector B of the injection computer and track 1 of the boost pressure control solenoid valve connector. Check the absence of breaks and short circuits on «mass» wires in the circuit between the 12 V circuit after the injection system relay and track 2 of the boost pressure control solenoid valve connector. Make necessary repairs if necessary.
Vacuum test
Connect the boost pressure control solenoid valve connector. Disconnect the hose coming from the solenoid valve from the pneumatic drive of the guide vanes. Attach a pressure gauge instead of the pneumatic drive, when the engine is idling.
If the vacuum at the hose outlet is greater than 750 mbar, check the boost pressure regulator flap.
Check the tightness of the damper on the seat in the extreme position.
Make sure the damper is at the stop at the maximum control signal.
Check the ease of movement of the actuator stem for the entire stroke.
If the problem persists, replace the turbocharger.
If the vacuum at the outlet of the hose is less than 750 mbar, check the vacuum at the inlet of the boost pressure control solenoid valve.
If the value is greater than 750 mbar, replace the boost pressure control solenoid valve.
If the value does not exceed 750 mbar, check the vacuum circuit and repeat the test, starting with checking the vacuum value.