Checking Vacuum System

Checking vacuum system

WARNING! Under no circumstances must the engine be turned on during this test!

Checking the function of the vacuum motor and the vacuum regulator and also that the valves can maintain negative pressure in the vacuum servo.

The check is carried out by running the vacuum motor and regulator with extra leads which are hooked up to the control module base. Be extra cautious as an incorrect connection may destroy components.

Make two cables






One is a single cable with flat pins at both ends, one of these flat pins being of the thin type.

The other is double lead joined at one end with flatpins of the ordinary kind, whereas both other ends have flat pins of the thin type.






Remove the cover from fuses and relays in the engine house. Remove the control module of the cruise control.

Start-up of vacuum pump and regulator






Connect single cable between 1S and 7T. Connect the other cable to 3S.
Ignition ON.
Connect a cable end to 9S, whereby a click should be heard from the vacuum regulator. Connect other cable end to 7S, which should start the vacuum motor while the vacuum servo contracts so that the control cylinder is pulled up. Remove cable from 7S when the vacuum servo is fully contracted, which will stop the vacuum motor.

In the event of a fault: see next step.






Allow the vacuum servo to be contracted for at least 30 seconds in order to check that there is no slip back, which would indicate a leak in the vacuum system.
Remove cable from 9S, which will release the vacuum servo. Ignition OFF.
If there are no faults: continue checking brake- and clutch-valve. See J7 below.
In the event of a fault: check under each heading below.






There is no click from the regulator or the pump does not start.
Use voltmeter to check ground on 3S and voltage on 1S.
There is ground and voltage: continue with next step below.






Check leads to and from vacuum motor and regulator.

Remove cables used for starting vacuum pump and regulator. Ohmmeter connected between 7T and 7S should indicate around 17 ohm (the internal resistance of the vacuum motor.)






Ohmmeter connected between 7T and 9S should show approx. 100 ohm (internal resistance of the regulator). Should there be a discrepancy in any measurement, take a measurement at vacuum pump~regulator in order to check if the fault is to be found in the cable harness or in the vacuum pump/regulator.

The vacuum system leaks.






Start vacuum pump and regulator as in J2 above. Stop the pump so it can be heard where it leaks.
If any of the valves are leaking and need adjusting, see trouble code 1-1-3.

Check that the brake and clutch valves disengage from the vacuum system.
Start vacuum pump and regulator according to J2 above. Stop vacuum pump when the vacuum servo is fully contracted (loosen at 7S) but keep the regulator connected.






Press brake pedal when vacuum servo should be released. In the event of a fault:

- Loosen tube connection and see that the vacuum servo releases
- Replace valve

Start vacuum pump again (connect 7S) in order to contract vacuum servo.
Press clutch pedal at which point the vacuum servo should release. In the event of a fault: replace valve.