Vacuum pump for cruise control?

[Kurt Deschler]

Try hooking the pump directly to the servo. That should confirm if the
pump is any good.

	-Kurt

> Message: 6
> Date: Tue, 27 Apr 2004 22:05:11 -0600
> From: Barry Babcock <barry at moonbeast.com>
> Subject: Vacuum pump for cruise control?
> To: quattro <quattro at audifans.com>
> Message-ID: <408F2D77.5090004 at moonbeast.com>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> Hi All-
>
> Still trying to fix the ailing cruise control on my 87 5kcstq.  Tony
> Hoffman suggested that my vacuum pump might be weak, because it won't
> pull the throttle body linkage all the way open--  This sounded like a
> very reasonable suggestion, so I tested it. (thanks Tony).  The linkage
> will open all the way using a hand pump- it takes between 5 and 6 in Hg
> to pull it all the way open (Is this right?).  The servo isn't leaking,
> I let it sit with the linkage retracted for quite awhile and it held the
> vacuum just fine.
>
> I'm using a new, leak free vacuum hose for all these tests.
>
> I went to a junkyard this afternoon and pulled two other vacuum pumps
> from wrecked 5000's, one turbo and one nonturbo (part number is the same
> it appears).  NEITHER of these pumps was able to do any better than the
> one that was previously in the car.  Maybe I just got two other bad
> ones, but I did the "run soapy water through the pump" trick and got the
> same results.
> The sides of the servo "suck in" but the linkage doesn't move.  I don't
> think it's a sticky valve-- if I compress the servo with my fingers,
> then release it, the spring will pull the linkage closed even with the
> vacuum pump running.
>
> Do these little vacuum pumps fail with alarming regularity like that?
>  Were they not up to the job to begin with?  They don't suck, and yet at
> the same time it appears that they do suck very much.
>
> Do I need to just bite the bullet and pay Rod at "thepartsconnection"
> the $140.00 for a new pump?
>
> Thanks for the help,
>
> Barry