The following is an easy procedure which I have followed to test the ‘mechanical’ elements of my cruise control system before I delve into the elektrickery side of things.
- Do a visual inspection of the vacuum pipes in the engine bay between the pump and the throttle control. Renew as appropriate.
- Remove the pump from it’s hiding place. See Haynes manual.
- If disconnected, reconnect the vacuum hose to the throttle bellows.
- Carefully remove the oval cover from the pump body.
- Prepare a 12v supply and connections. ,
- Connect a positive12v supply to the left hand terminal as shown.
- Whilst observing the solenoid in the housing tapthe negativeconnection on the righthand terminal. Solenoid (vac dump valve) should operate. (If it doesn’t the solenoid is kaput).
- Next connect the negativeto the upperterminal and the pump motor should run. (If it doesn’t the motor is kaput).
- Whilst observing the bellows at the throttle gently press down on the top of the solenoid (see image) and the bellows should collapse strongly into the metal cup. (If it doesn’t either the pump diaphragm, the bellows or the footbrake dump valves are kaput).
- To isolate the footbrake valve simply clamp the vac hose from the vac hose t piece and repeat 9 above. (If the bellows collapses fully the footbrake valve is at fault. If the bellows doesn’t collapse it’s either the bellows or the pump).
- To check the pump disconnect it from the vac hose and connect a simple vac gauge (a few quid from a motor factors) to it. The one that I tested which pulled the bellows fully in registered 20 in. Hg.
