[Acesanugal]

'91 Jetta GL (German car, if that makes a difference)
It's got cruise control...what I assume to be a factory option as it's on the turn signal stock and not a separate switching unit drilled into the side of the steering column garnish.
It doesn't work... The diaphragm holds air (I sucked on it's vacuum line and it maintains pressure). The vacuum line looks like it was replaced no more than a year and a half ago and runs all the way to the firewall where it's attached to a little black round thing wit a set of plastic nipples on it. This unit is under the (round) coolant reservoir. The vacuum line from the diaphragm is connected to the nipple on the left, towards the motor. The nipple on the right has NOTHING connected to it.
The idle is crappy and surges about 100rpm when warm.
Is there anything that's supposed to be connected to the nipple on the right? Should it be capped off?
Pedal assembly: The vacuum line(s) I found were firmly attached to their nipples.
I will take a pic of the vacant nipple and the unit itself if need be. Just let me know. I'll be up 'till 4am EST

 

[under the radar]

the black round thing is called a vacuum amplifier. yes there should be a vacuum line connected to all the fittings on it. your hood should have a vacuum diagram sticker on the inside.
edit: uh, oops sorry, disregard what i said, i' missed that this was an 8v, thought we were talking about 16v.


Modified by under the radar at 1:05 AM 12-1-2007

 

[Acesanugal]

Well, I found the vacuum diagram but it doesn't seem to be helping. Haha
Could the bare nipple be for an accessory I don't have? Such as the shift-up light? Maybe it was capped off at one point but they came off?

 

[compu_85]

Re: (Acesanugal)

The nipple on the right shouldn't have anything hooked to it.

The bently manual has a troubleshooting tree for the cruise system.
-Jason

 

[Acesanugal]

Then shouldn't it be capped off to avoid a massive vacuum leak...?

 

[Acesanugal]

Re: (compu_85)

I don't think the system is routed right... Here are pics. Follow the vac line from the diaphragm (servo) to the amplifier.

 

[Ajent]

Re: (Acesanugal)

usually on these cars the servo pump isn't getting power. Or it's seized. Try feeding it power and see if it forms a vacuum

 

[Acesanugal]

The 'servo pump' as you said...is that the 'amplifier' shown in my pic? 'cuz the only vacuum hose the diaphragm is connected to is the 'amplifier'.

 

[bubu1]

Re: (Ajent)

These systems never worked even when new we had problems with them.

 

[compu_85]

Re: (Acesanugal)

Ya, it's not an amplifier, it's it's own pump. The open nipple is how it vents off the vacuum to release the throttle. The cruse system is completely separate from the engine vacuum system.

 

[compu_85]

Re: (compu_85)

 

[Acesanugal]

Oh, okay, I see now. I think...
So starting from the diaphragm itself...
The diaphragm, which is connected to the (hand bone!) throttle. One vacuum line runs from that, all the way to the pump where it is connected to the left nipple. The right nipple is the vent to release the throttle when the system is deactivated by the switch, depressing the brake or the clutch pedals.
The y-fitting before the hose from the diaphragm meets the pump goes thru the firewall and into another y-fitting, where it is split between the switches for the clutch and brake?
Am I correct, or am I, as the title says, 'missing something'?

 

[Acesanugal]

To test the operation of the pump:
Terminal 4? Sorry, not sure how to read electrical **** like that. Translation...?
To be honest...me + electrical systems = No go

 

[VDub2625]

Re: (Acesanugal)

You are correct.
The cruse control computer is behind the center console. The terminals are very clearly labeled on the housing. Get a jumper wire and get to work.