Supplementary Information

This describes fault tracing and adjustment procedures of the vacuum system for 1986 M/Y -> electronic cruise control.

Check that fuse #1 is okay.
Check that the brake lights work and that the brake light switch is correctly adjusted.
The control unit is grounded via the brake lights. If both brake light bulbs are blown, the control unit will not function.

The brake lights should come on when the pedal is depressed 8-14 mm (0.3-0.6 in) before the brakes are applied. Adjust if required.

Remove underdash panel from driver's footwell.

Check that air valves at brake and clutch pedals are correctly adjusted and do not leak.
The valve should be closed when the pedals are up and open when the pedals are depressed.
Test each valve by connecting a hose to it and blowing through.
Adjust if required.

Check that vacuum servo hoses and air valve hoses are correctly connected and not kinked.

Make sure that vacuum hose connected to intake manifold is not blocked or punctured.

Disconnect hose from connection marked VACUUM on valve housing.
Start engine and place thumb on end of hose. Suction should be felt.
No suction: check hose and connection to intake manifold.
Reconnect hose.

Start engine and leave running for about 30 seconds to establish vacuum.

Turn engine OFF.

Disconnect hose from valve housing connection marked VACUUM. A hiss should be heard.
No hiss indicates a leak in cruise control vacuum system.
(Vehicles with CU heater: leak might occur from heater shutter valve vacuum system.)
Reconnect hose to valve housing.
To find out if leakage is from CU system or cruise control system, pinch hose indicated by arrow and start engine to establish a vacuum.
Turn engine OFF after 30 seconds.
Disconnect hose from connection marked VACUUM on valve housing. If a hiss is heard this indicates that the CU heater vacuum system is leaking. No hiss indicates that the cruise control vacuum system is leaking.
Correct as required and recheck.

Reinstall underdash panel (arrow)