Vacuum Advance Control Solenoid: Testing and Inspection

CHECKING VACUUM ADVANCE CONTROL

Troubleshooting Vacuum Advance Control System:

- Take off protective cap.
- Remove advance control relay and pull off plug.





- Connect relay (3) and plug (4) on advance control simulator 12 1 460.
- Set switch (1) on simulator to position A.





- Connect BMW service test unit or BMW digital tester.
- Perform engine test step 06 or check ignition timing.
- The ignition timing value displayed now will be "retarded" approx. 20° on crankshaft by the simulator.





- Lamp "MV" on the simulator comes on - the solenoid is activated.
- Hose (1) is vented (cap 4).
- 1 To advance control box on distributor.
- 2 To intake air manifold or throttle housing
- 3 Electric activation of simulator





- Lamp "tp" (load signal) will flash throughout the entire test.





- Perform test steps A through D according to procedures printed on the simulator.

Example:
- Switch 1 set to position D.
- Switch 2 set to position O.

- Lamp MV not on, so that this means the advance control box has vacuum.
- Refer to troubleshooting chart for vacuum advance control, if the specified conditions are not found in the tests.





- The resistance values for the coolant temperature and intake air temperature transmitters can be taken at the jacks.

G = Ground
TW = Water temperature
TA = Intake air temperature





- If the coolant temperature switch is checked at a temperature below 45°C (113°F), pull off plug on idle control unit (in glove box above L-Jetronic control unit).





- Check resistance on coolant temperature switch.





- Check resistance* on intake air temperature switch.
- The switches should be connected during the check with control simulator.