(M) Testing Vacuum System

M. Vacuum System Test

WARNING: DO NOT START ENGINE UNDER ANY CIRCUMSTANCES DURING THIS TEST.

Test the vacuum motor and regulator function and ability of valves to hold vacuum in vacuum servo. Test is performed by operating vacuum motor and regulator with extra cables connected to control unit connector. Use extra caution to ensure that improper connections do not damage components. Perform an additional visual inspection of diaphragm and seals at seams.

Make two cables, one is a single cable with tab terminals at both ends, one of the narrow type. The other consists of two cables with two ordinary flat connectors at one end and two narrow tab terminals at the other end. The test begins with M1.


M1. Ground Cable Test






Ignition off.
Disconnect control module.
Terminal 3B and ground.
The ohmmeter should display about 0 ohm.

If reading is OK:
Power supply test M2.

If reading is incorrect:
Check cable between control module terminal 3B and ground for breaks, according to QA2. (Q) Other Electrical Fault Tracing


M2. Power Supply Test






Control module disconnected.
Ignition on.
Connect a voltmeter between control module socket terminal 3B and terminal 1B. Voltmeter should display battery voltage.

If reading is OK:
Regulator function test M4.

If reading is incorrect:
Fuse check M3.


M3. Fuse Check






Check that fuse 19 in the central electronics module (inside the car) is intact.

If fuse is intact:
Check the cable between fuse 19 and control module for breaks, according to QA2.


If fuse is blown:
Check cables between: fuse 19 and switch terminal 2, fuse 19 and control module terminal 1B, vacuum pump terminal 3 and control module terminal 7E, switch terminal 1 and brake valve.

Automatic transmission: brake valve and control module terminal 9E, manual transmission: brake valve and clutch valve, manual transmission: clutch valve and control module terminal 9E.

Switch terminal 3 and control module terminal 6E, switch terminal 4 and control module terminal 8E, switch terminal 5 and control module terminal 4E for short circuit to ground, according to QA3.


M4. Regulator Function Test







Disconnect control module.
Ignition on.
Connect the single cable between control module socket terminal 1B and terminal 7E.

Connect the other cable with the double tab terminals to control module socket terminal 3B, and one of the other ends to terminal 9B. A click should be heard from the regulator.

If a click is heard:
Vacuum pump function test M11.

If no click is heard:
Test line to regulator M5.


M5. Test Of Line To Regulator






Ignition off.
Control module connected.
Vacuum pump disconnected.
Using an ohmmeter, measure the resistance between vacuum pump connector terminal 1 and ground.
The ohmmeter should read about 3.5 M ohm..

If reading is OK:
Check of line to vacuum pump M7.

If ohmmeter reads about 0 ohm:
Check cable between vacuum pump terminal 1 and control unit terminal 9B for short circuit to ground according to QA3.

If ohmmeter displays infinite resistance:
Test of regulator power supply M6.


M6. Test Of Regulator Power Supply






Ignition off.
Control module connected.
Vacuum pump disconnected.
Ignition on.
Using a voltmeter, measure the voltage between the vacuum pump connector terminal 1 and ground.
Voltmeter should display about 10 volts.

If reading is OK:
Check of cable to vacuum pump M7.

If reading is incorrect:
check line between vacuum pump terminal 1 and control module socket terminal 9B for breaks, according to QA2.


M7. Check Of Cable To Vacuum Pump.






Ignition off.
Control module connected.
Vacuum pump disconnected.
Using an ohmmeter, measure the resistance between vacuum pump connector terminal 3 and ground.
The ohmmeter should read about 2.5 M ohm.

If reading is OK:
Vacuum pump function test M12.

If ohmmeter displays about 0 ohm:
Check cable between vacuum pump terminal 3 and control unit socket terminal 7E for short circuit to ground, according to QA3.

If ohmmeter displays infinite resistance:
Test of vacuum pump power supply M8.


M8. Test Of Vacuum Pump Power Supply






Ignition off.
Control module connected.
Vacuum pump disconnected.
Ignition on.
Using a voltmeter, measure the voltage between vacuum pump terminal 3 and ground. Voltmeter should display about 0 volts.

If reading is OK:
Line resistance test M9.

If reading is incorrect:
Check cable between vacuum pump terminal 3 and control unit socket terminal 7E for short circuit to supply, according to QA4.


M9. Line Resistance Test






Ignition off.
Disconnect control module.
Vacuum pump disconnected.
Using an ohmmeter, measure the resistance between vacuum pump connector terminal 3 and control module socket terminal 7E.
The ohmmeter should display about 0 ohm.

If reading is OK:
Regulator test M10.

If reading is incorrect:
Check the cable between vacuum pump connector terminal 3 and control module socket terminal 7E for breaks, according to QA2.


M10. Regulator Test






Ignition off.
Disconnect vacuum pump.
Using an ohmmeter, measure resistance between terminals 1 and 3 on the vacuum pump. The ohmmeter should display about 100 ohm.

If reading is OK:
Service control module connector and vacuum pump connector for contact resistance and oxidation, according to QA5, and for loose connections, according to QA5.

If reading is incorrect:
Try a new vacuum pump.


M11. Vacuum Pump Function Test






Ignition on.
Connect the single test lead between control module socket terminal 1B and terminal 7E. Connect the other cable with the double flat pin to control module socket terminal 3B, and one end to control module connector terminal 9B. A click should be heard from the regulator.
Connect the other free end to control module socket terminal 7B.

The vacuum pump should then start and the vacuum servo should pull the throttle control to fully open. Wait about 30 seconds.
If the vacuum servo has not released the throttle control at all after 30 seconds, there are no leaks in the vacuum system.
Disconnect the lead that is connected to control module socket terminal 7B. The vacuum pump should stop.

If the vacuum pump is OK and does not leak:
Brake valve test M16.

If vacuum system leaks:
Check hoses to vacuum pump and vacuum servo for leaks.
Proceed with: Brake valve test M16.

If vacuum pump is not OK:
Test line to vacuum pump M12.


M12. Test Of Line To Vacuum Pump






Ignition off.
Disconnect vacuum pump.
Control module connected.
Using an ohmmeter, measure resistance between vacuum pump connector terminal 2 and ground.
The ohmmeter should display about 3000 ohm.

If reading is OK:
Vacuum pump test M15.

If ohmmeter reads about 0 ohm:
Check cable between vacuum pump terminal 2 and control unit terminal 7B for short circuit to ground according to QA3.

If ohmmeter displays infinite resistance:
Vacuum pump power supply test M13.


M13. Vacuum Pump Power Supply Test






Ignition off.
Control module connected.
Vacuum pump disconnected.
Ignition on.
Using a voltmeter, measure the voltage between vacuum pump connector terminal 2 and ground. Voltmeter should display about 0 volts.

If reading is OK:
Line resistance test M14.

If reading is incorrect:
Check the cable between vacuum pump terminal 2 and control module socket terminal 7B for short circuit to supply, according to QA4.


M14. Line Resistance Test






Ignition off.
Disconnect control module.
Vacuum pump disconnected.
Cables disconnected.
Using an ohmmeter, measure resistance between vacuum pump connector terminal 2 and control module socket terminal 7B.
The ohmmeter should display about 0 ohm.

If reading is OK:
Service control module connector and vacuum pump connector for contact resistance and oxidation, according to QA6, and for loose connections, according to QA5.

If reading is incorrect:
Check the cable between vacuum pump terminal 2 and control module socket terminal 7B for breaks, according to QA2.


M15. Vacuum Pump Test






Ignition off.
Vacuum pump disconnected.
Using an ohmmeter, measure resistance between vacuum pump connector pins 2 and 3. Ohmmeter should display about 10 ohm.

If reading is OK:
Service the vacuum pump connector for contact resistance and oxidation, according to QA6, and for loose connections, according to QA5.

If reading is incorrect:
Try a new vacuum pump.


M16. Brake Valve Test






Ignition on.
Connect the single cable lead between control module socket terminal 1B and terminal 7E.
Connect the other cable with the double flat pin to control module connector socket terminal 3B. Connect one of the other ends to control module socket terminal 9B. A click should be heard from the regulator. Connect the other free end of the cable to control unit socket terminal 7B.

The vacuum pump should start, and the vacuum servo should pull the throttle control to fully open. Stop the vacuum pump when the vacuum servo has reached its full travel limit, by removing the lead from control module socket terminal 7B. Depress brake pedal. Brake valve should open the system to the atmosphere and the vacuum servo should release.

If function is OK:
Manual transmission: Clutch valve test M18.
Automatic transmission: vacuum system test completed.

If function is not OK:
Brake valve adjustment M17.


M17. Brake Valve Adjustment






Ignition off.
Disconnect cables.
Remove hose connections so that vacuum servo releases.
Valves should be closed and must not leak when pedals are up.
Depress pedal so that it does not contact the valve.
Pull out piston as far as possible and release pedal slowly.
Plastic tabs in valve will then hold piston in correct position.

If brake valve is OK:
Manual transmission: Clutch valve test M18.
Automatic transmission: Vacuum system test completed.

If brake valve is not OK:
Manual transmission: try a new brake valve and continue with clutch valve test M18. If, automatic transmission: try a new brake valve.


M18. Clutch Valve Test






Ignition on.
Connect the single cable lead between control module socket terminal 1B and terminal 7E.

Connect the other cable with the double flat pin to control module socket terminal 1B. Connect one of the other ends to control unit socket terminal 9B. A click should be heard from the regulator.
Connect the other tree end of the cable to control unit socket terminal 7B.

The vacuum pump should start and the vacuum servo should pull the throttle control to fully open. Stop the vacuum pump when the vacuum servo has completely drawn down, by removing the lead from control module socket terminal 7B. Depress clutch pedal. Clutch valve should open the system to the atmosphere, and the vacuum servo should release.

If function is OK:
Vacuum system test completed.

If function is not OK:
Clutch valve adjustment M19.


M19. Clutch Valve Adjustment






Ignition off.
Disconnect cables.
Remove hose connections so that vacuum servo releases.
Valves should be closed and must not leak when pedals are released.
Depress pedal so that it does not contact the valve.
Pull out piston as far as possible and release pedal slowly.
Plastic tabs in valve will then hold piston in correct position.

If clutch valve is OK:
Vacuum system test completed.

If clutch valve is not OK:
Try a new clutch valve