Bad vacuum pump?

[rogerzr1]

I took the z out for a short run this afternoon. Everything was great untill I stopped to top off the tank. When I got back in the car and turned the key there was no vacuum pump sound. The car cranked and I drove it home but the secondaries were not working. Now at home when I turn the key on the pump cycles for less than a second and shuts down. Please help.
Thanks, Roger.

[xlr8nflorida]

Originally Posted by rogerzr1

I took the z out for a short run this afternoon. Everything was great untill I stopped to top off the tank. When I got back in the car and turned the key there was no vacuum pump sound. The car cranked and I drove it home but the secondaries were not working. Now at home when I turn the key on the pump cycles for less than a second and shuts down. Please help.
Thanks, Roger.

The pump should shut off, its not supposed run all the time or you have a vacuum leak.

You should check connections on the pump which sits by the overflow radiator tank. Also make sure the thin black wire which goes to the plenum is connected. What I mean by that is that is not one line but two pieces together. You will see where the line gets fatter, that is where they connect together. Make sure they are firmly inside one another.

Do you have any SES lights? If so and there are codes, secondaries won't work.

The secondary pump is really just to assist for high rpm extended high speed runs. The secondaries should still work even with that pump not working. Perhaps you have issue with vacuum leak. You can test it with a mityvac pump.

This article is very helpful:

http://www.corvetteactioncenter.com/...0/002/article/

Good Luck!

[rogerzr1]

That is a good article. It says that the pump should prime 5-10 seconds when the key is turned on. After this afternoon mine only stays on for less than a second.

[xlr8nflorida]

Originally Posted by rogerzr1

That is a good article. It says that the pump should prime 5-10 seconds when the key is turned on. After this afternoon mine only stays on for less than a second.

I noticed that too, mine never stays on anywhere near that long.

A second or two for mine. My car has been like that for 10 years.

LT-5 runs like a Beast! Maybe others can chime in on how long their pump stays on??

If that pump is bad, go with the vacuum pump from a Kodiak. If you have 90, you will need to switch out plug, 91-95 plug and play. You will save yourself a few hundred bucks that way.

I think you have another issue though then the secondary pump, ses code or vacuum leak under plenum.

PS Where in GA?

[Paul Workman]

To put your mind at ease over the pump, you can disconnect the vacuum line at the coupling where it goes under the plenum, and with the ignition switch "ON", the pump should start running and continue to run. By putting your thumb over the end of the vacuum line, the pump should shut off in about a second or so. If the pump quits before you plug the tube with your (thumb), then the pump and associated switch come under suspicion.

However, as mentioned, the pump only provides initial vacuum charge at start-up and will sustain vacuum under prolonged WOT situations. Otherwise, the plenum vacuum will maintain the vacuum and actuate the secondaries and the pump remains shut down.

If the test with your thumb proves the pump is functioning properly, it can also be assumed the integrity of the vacuum circuit up to the vacuum solenoid is not leaking (or the pump would not be shutting off). (see below)




Did you get an SES light when the secondaries should have opened?

If YES, then there is a vacuum circuit failure which may include the vacuum solenoid and all components up to and including the differential pressure switch. A miti-vac will be helpful to isolate a vacuum leak, if there is one. (Make sure the secondary actuators operate freely. As mentioned many times before, some actuators were installed incorrectly at the factory, resulting in the actuator rod pulling at a angle instead of in line with the secondary linkage.) If there is no vacuum leak, the differential pressure switch can be dismissed too (the diff. pressure switch signaled "no vacuum" and consequently the SES light, and the vacuum solenoid and it's connection are next (and last).

If NO SES light then the vacuum circuit integrity is intact, and the secondary actuators come under suspicion. A miti-vac pump will quickly show you if you have a failure to actuate!

Just so much one can do w/o seeing what is going on. But, hopefully this will get ya started. Personally, I opted to toss the entire secondary headache - vacuum lines, check valves, pumps, actuators, etc, etc, including the throttle plates and all hardware. Unless you're running an NCRS car, you'll never miss 'em. In fact, you may discover you like the responsiveness and the freedom from every worrying about it again. But, you'll need a chip that has been prepped for running sans secondaries; Marc Haibeck can accomodate. I believe you won't regret taking the plunge! (Most all of the FBI gang is running secondary free, and the number continues to grow!)

Just an aside... When first turning the ignition switch to on, and before rolling it over to actuate the starter, you should see the SES (among other) lights come on for a second or two - part of the ECM and bulb test. If there is no SES then, well I would want to get that fixed right away!

This would be a good stopping point. Continuing to play "what if" without specific additional results from troubleshooting will just lead to that overwhelming morass of confusion...

Check it out and get back!

FWIW,
P.

[rogerzr1]

Did you get an SES light when the secondaries should have opened?

If YES, then there is a vacuum circuit failure which may include the vacuum solenoid and all components up to and including the differential pressure switch. A miti-vac will be helpful to isolate a vacuum leak, if there is one. (Make sure the secondary actuators operate freely. As mentioned many times before, some actuators were installed incorrectly at the factory, resulting in the actuator rod pulling at a angle instead of in line with the secondary linkage.) If there is no vacuum leak, the differential pressure switch can be dismissed too (the diff. pressure switch signaled "no vacuum" and consequently the SES light, and the vacuum solenoid and it's connection are next (and last).

If NO SES light then the vacuum circuit integrity is intact, and the secondary actuators come under suspicion. A miti-vac pump will quickly show you if you have a failure to actuate!

Just so much one can do w/o seeing what is going on. But, hopefully this will get ya started. Personally, I opted to toss the entire secondary headache - vacuum lines, check valves, pumps, actuators, etc, etc, including the throttle plates and all hardware. Unless you're running an NCRS car, you'll never miss 'em. In fact, you may discover you like the responsiveness and the freedom from every worrying about it again. But, you'll need a chip that has been prepped for running sans secondaries; Marc Haibeck can accomodate. I believe you won't regret taking the plunge! (Most all of the FBI gang is running secondary free, and the number continues to grow!)

Just an aside... When first turning the ignition switch to on, and before rolling it over to actuate the starter, you should see the SES (among other) lights come on for a second or two - part of the ECM and bulb test. If there is no SES then, well I would want to get that fixed right away!

This would be a good stopping point. Continuing to play "what if" without specific additional results from troubleshooting will just lead to that overwhelming morass of confusion...

Check it out and get back!

FWIW,
P.[/QUOTE]


One thing I didn't mention is that the car died shortly after I started it after getting gas. After I restarted it it didn't try to cut out anymore. I don't know if this matters.

I did not get a SES light and I checked and the light does function. I am going to take the car back out this afternoon and see if it is still acting up.

I would prefer to take the entire secondary system off of the car even if it is not the problem right now eventually it will cause problems. How much does it cost to take the system off and how hard is it to do?

Thanks guys.