Vacuum Pump

[dan1495]

Last weekend I replaced the leaking oil pressure sensor on my 90 which involved removing the oil filter adapter. The car runs fine but I noticed the vacuum pump under the right headlight is acting differently. When I first turn the key on the pump runs for a few seconds and shuts off like it did before. Now however, after the intial cycle the pump keeps cycling on and off every few seconds. This stops as soon as I start the car.The vacuum pump line to the plenum has a splice - I don't know if this is normal or not - but the line came apart during the the latest repair job. The weird thing is that when I separate the vacuum line at the splice the pump runs constantly as you would expect. When I block the line going to the pump it starts to cycle again like it does when everything is connected. If the line had a leak I would think the pump would always run. Anyone have any ideas?

[secondchance]

Originally Posted by dan1495

Last weekend I replaced the leaking oil pressure sensor on my 90 which involved removing the oil filter adapter. The car runs fine but I noticed the vacuum pump under the right headlight is acting differently. When I first turn the key on the pump runs for a few seconds and shuts off like it did before. Now however, after the intial cycle the pump keeps cycling on and off every few seconds. This stops as soon as I start the car.The vacuum pump line to the plenum has a splice - I don't know if this is normal or not - but the line came apart during the the latest repair job. The weird thing is that when I separate the vacuum line at the splice the pump runs constantly as you would expect. When I block the line going to the pump it starts to cycle again like it does when everything is connected. If the line had a leak I would think the pump would always run. Anyone have any ideas?

It sounds like you might have a tiny leak between the splice and the pump.

[scottfab]

Originally Posted by dan1495

When I block the line going to the pump it starts to cycle again like it does when everything is connected. If the line had a leak I would think the pump would always run. Anyone have any ideas?

The pump over time can suck in lots of dirt. This interferes with the pump's rubber internal seal. With care the pump can be taken apart and cleaned. Then you have to glue it back together. I have rebuilt mine twice. Never did do a "How to" on this.

[tpr60]

Scott,

I have had my pump motor partially apart, any tips on getting the the internal pump/motor apart. My pump doesn,t put out enough vacuum to activate the shutoff switch. Currently using a Ford diesel vacuum pump that works great except the electrical connection is different.

[scottfab]

Originally Posted by tpr60

Scott,

I have had my pump motor partially apart, any tips on getting the the internal pump/motor apart. My pump doesn,t put out enough vacuum to activate the shutoff switch. Currently using a Ford diesel vacuum pump that works great except the electrical connection is different.

I've searched without luck for pics of when I did this work. Evidently I thought it to be insignificant enough not to take any.

Here's what I remember. The area of interest is the little puck shaped part where the vacuum tubes connect. The other larger part is just the motor and electrical connector.
Carefully pry back on the plastic that goes around the center circular part.
It's not very well glued from the factory. In there you'll see loads of dust and crap. Clean and reassemble. I tried using a a pipe clamp to hold it back together. That leaked so I re-glued it.

[Hammer]

Your leak could also be the check valve under the plenum.

[scottfab]

Originally Posted by Hammer

Your leak could also be the check valve under the plenum.

He has isolated the plenum by opening the line and blocking it going into the pump.

[Paul Workman]

In the mean time, the leak is slow enough to indicate it is very small, and vacuum is sufficient for the SPTs to operate, especially when the motor is running. So, it can take a back burner to perhaps other items on your "to do" list.

Geeze...Wish I had a dollar for every time there is a thread that is secondary vacuum related...Just sayin

P.

[dan1495]

I agree it is a minor issue that can be addressed as time permits. I did try a search before I posted the question but didn't find anything that helped. I am still trying to learn about these cars, so I apologize if I ask questions that have been asked many times before.

[VetteMed]

Originally Posted by dan1495

I agree it is a minor issue that can be addressed as time permits. I did try a search before I posted the question but didn't find anything that helped. I am still trying to learn about these cars, so I apologize if I ask questions that have been asked many times before.

No reason to apologize, we are happy to help newcomers to the ZR-1 brotherhood. I think Paul's comment was in reference to the fact that he, and I, and many others, have entirely deleted the secondary system, and therefore don't have to troubleshoot it anymore

Andrew