Vacuum pump for cruise control?

[Barry Babcock]

Oops- That's what I did in testing the pump last night- I tested all 
three pumps by connecting them with a single vacuum hose directly to the 
servo.

Sorry if that was unclear in my last post.  No leaks, just about two 
feet of vacuum line between pump and servo.  None of the three pumps 
could retract the linkage.

I guess what I'm wondering is:

1) Should a good pump be capable of easily retracting the linkage (I 
take it the answer to that question is yes).

2) How much vacuum (inches of Hg, psi, whatever) should be required to 
pull the linkage back?  I don't know if you even can adjust the spring 
tension in the throttle valve.

3) Is there any way I can make one of these pumps work by 
replacing/refreshing some commonly worn out internal part, or should I 
start looking for yet another pump, new or used?

Thanks again for your responses.

-Barry


Kurt Deschler wrote:

>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
>>    
>>