Hi all. Just a few questions about the vacuum pump used in '90's Magna cruise control systems and, consequently, how does the CC system in later model Magna's work (in terms of pump operation)? I want to use it another application as a source of variable vacuum, so...

The pump I have is from a '94 model but I did see the same pump used in other models

There are 4 wires into the pump; blue, pink w'red trace, green and yellow. What are each of them for? I am assuming that at least one pair will be for pump motor windings but which 2 wires and what is the second pair for? Perhaps a bleed control solenoid, or a second set of motor windings ie. motor/pump speed control? If it is a bleed control solenoid, what frequency does it operate at?

What is a typical, perhaps maximum, vacuum that the pump can generate?

Does the pump run continuously or start and stop?

OK, I pulled the cover off the bottom of the pump and found:

One power wire: pink/red = white/red on the car harness

An earth for the pump motor: yellow = blue/red on the car

Two solenoid wires, earths I presume: blue = blue/yellow on the car and green = blue/black on the car.

What do the solenoids do? I have tried powering the motor (it works :) ) and earthing the solenoids (they "click") but it's still not very clear as to what they actually do. Does one bleed vacuum and the other atmospheric pressure to the throttle actuation diaphram or what?

Anyone know?

Typical vacuum would be about 22 InHg (basic engine vacuum on downhill decel). I dont do KPA so no idea of that.

Lots of questions...

I would suggest downloading the service manual - there are a few places. Has the full wiring diagram.

Thanks for the reply. A wiring diagram would be perfect if you would point me in the right direction to find one.

The inches of Mercury is OK, I can convert :) .

Here is the diagram - it isn't all that conclusive (all handled by the ECU) but gives you an idea what the wires are for.

Thankyou! That is exactly what I was after. It does look like when the blue/black (L-B) wire is earthed by the ECU, the vacuum is applied to the throttle actuation diaphram, when the black/yellow (L-Y) wire is earthed, a port to atmospheric pressure is opened.

I guess the frequency with which the solenoids are pulsed (if they are indeed pulsed) and the duty cycle of the pump (I don't want to kill the pump by running it continuously if it isn't designed to do that) is harder?

If you, or anyone else for that matter, has CC, can the vacuum pump and/or solenoids, be heard operating while the cruise control is activated? I suspect that engine and road noise, and sound deadening may make that difficult, but I'm asking anyway.

If you, or anyone else for that matter, has CC, can the vacuum pump and/or solenoids, be heard operating while the cruise control is activated? I suspect that engine and road noise, and sound deadening may make that difficult, but I'm asking anyway.

you can't.

you can't.

Does that mean you can't hear it because it's not operating, or that you can't hear it because there's too much noise?

Does that mean you can't hear it because it's not operating, or that you can't hear it because there's too much noise?

Too much road noise etc.