Vacuum pump running

[Dime]

I've got an interesting one I think. A few weeks ago I started up my z to let the fluids get circulated and burn off some condensation. Cars been sitting a lot lately. I started the car as I always do. Turned the power on and let everything prime before starting the car. Usually the vacuum pump runs a few seconds like always, priming the system. Well, this time it came on and did not turn off. Even with the engine running, it ran continuously. The car had a little trouble starting, but nothing major. I chalk that up to it having been sitting a few weeks.

The engine didn't idle high or low. No sputters, nothing that was out of the ordinary. I didn't take if for a drive because I didn't have the time. Well, this weekend I had a little time to go mess with the car. This time everything behaved as it always has. Turn the power on, vacuum pump runs a few seconds, shuts off. I even turned the car on and off a couple times and the pump didn't even come on to re prime the system, and if it did, it was for a second or less. Car started fine and held a vacuum.

What could have been the deal? I will say that when the pump was running continuously, it was a few weeks ago when the temperature dropped like a rock. May that have had something to do with it? I've never had any vacuum problems before. I know that they can pop up suddenly, but go away suddenly as well?

Thanks guys

[Kevin]

Mines doing the same thing. I'm stumped

[Hib Halverson]

Have you guys leak tested your secondary vacuum system?

[XfireZ51]

Guys,

When the weather turns cold, my tires will lose pressure. It may be a case of something shrinking faster than something else. Then everything stabilizes.
As Hib suggested, I would do a quick vacuum test. Perhaps even the secondary vacuum solenoid may have been stuck and then freed up once warmed..

[Kevin]

Have you guys leak tested your secondary vacuum system?



I did. And it tests fine but sets a low vac code. It it did. Last time I drove it, ran fine.

[Hib Halverson]

"low vac code".

Code 56?

[Kevin]

"low vac code".

Code 56?

Sounds about right.

[RIP]

there's a vacuum-electric switch that is probably sticking. Try tapping on a running vacuum pump when the engine is running.

[Paul Workman]

Third time was the charm on mine for that nonsense: Strike THREE! Now it NEVER comes on! (& You can guess why not! :D)

[Dime]

Third time was the charm on mine for that nonsense: Strike THREE! Now it NEVER comes on! (& You can guess why not! :D)

It's been on the list...

[PhillipsLT5]

Third time was the charm on mine for that nonsense: Strike THREE! Now it NEVER comes on! (& You can guess why not! :D)

yep, not on car, in parts bin, works for me also

[Kevin]

giving serious consideration to that.

[GOLDCYLON]

And never looked back

[XfireZ51]

giving serious consideration to that.

You can do this without removing anything if you want to keep things reversible. Just strap the secondaries open, and make the prom calibration changes for the mod. If the motor is modded, you would likely need to tweak the fueling tables for part throttle and cruise operation.

[Kevin]

You can do this without removing anything if you want to keep things reversible. Just strap the secondaries open, and make the prom calibration changes for the mod. If the motor is modded, you would likely need to tweak the fueling tables for part throttle and cruise operation.

I've talked with Mark Haibeck about this a few times and I'm really considering it. The cost is what's holding me back.

[Dynomite]

I have one ZR-1 with secondaries removed and three ZR-1s with secondaries functioning perfectly.

The TRICK to a fun to have secondary system is a vacuum system with no leaks.

The TRICK to diagnosing/fixing/having a vacuum system with no leaks is Blocked TB Coolant at the Injector Housings. Eliminated IH Housing and Throttle Body (TB) Coolant system Tricks (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-2.html#post1581460754)

With TB Coolant blocked you do not need any sealant on the Plenum Gasket and Plenum Removal is essentially a ten minute no mess maintenance function. Removing Plenum (including the 10 minute Plenum Removal) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-4.html#post1581663365)

Most Importantly, Removing the Plenum with TB Coolant Blocked will not involve Coolant in any regard (removal or filling Coolant).

Once the Plenum is Removed vacuum leaks can easily be found and corrected.
Checking for Vacuum Leaks TIPS (http://www.zr1.net/forum/showthread.php?p=187897)

Having an Operational Secondary Full Power Switch (http://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-8.html#post1587653767)