How Much Secondary Leakage?

[Schrade]

Since I ripped & kludged [sp?] 'em out, I won't vote (just for you there Scott ).

But I had timed mine to 1-2 sec's every 12-15 sec's, when I posted up about it...

Originally Posted by scottfab

This is not normal. 10sec is too short of an interval.
It's easy to get it to 30sec or more.

DON'T rip it all out !
Just fix it like you would a burned out light bulb.
You also should not trade the car in for a new one
when the ash tray is full.

Start with the basics.
Find the hard plastic hose that comes out of the pump and
pull it out. Then put you finger over the side coming from the pump.
It should run a bit then stop for an indefinite period of time.
Report back then we can direct you to the next step.
(or find the old thread that covers this to send you too)

[scottfab]

Originally Posted by Schrade

Since I ripped & kludged [sp?] 'em out, I won't vote (just for you there Scott ).

But I had timed mine to 1-2 sec's every 12-15 sec's, when I posted up about it...

I try not to use terms like "kludge" and "ripped" out anymore. Some people find them upsetting and/or condescending along with "rattle can" and "wonky"
It's a "kinder gentler" world.
(click on each word for a deffinition)

[scottfab]

So far the average (leakage) time between cycles would seem to be greater than 5sec, much greater.

[weldbead]

moderator:
sorry i screwed it up.. i voted for greater than 30 seconds..in fact my pump runs(i stopped timing it after 60 seconds)

[Paul Workman]

Originally Posted by weldbead

moderator:
sorry i screwed it up.. i voted for greater than 30 seconds..in fact my pump runs(i stopped timing it after 60 seconds)

> 30 sec would include 60+ I would think. In any case you have a significant leak that requires attention.

Using a Mitivac (hand vacuum pump) one can isolate the problem fairly simply.

Here's a schematic of a 90, but the other years are quite similar, except the MAP switch is located under the ECM on the 90, but is under the plenum on 91+ cars.



The place to start is with the rubber connector on the plastic vacuum line, located on the plastic line, just as the line goes under the plenum. Pull it apart and put your thumb over the end of the tube. If the vacuum pump shuts off, then the problem is under the plenum (sorry). Otherwise the pump itself or the tubing or check valve is suspect.

Once under the plenum, you can use a Mitivac to apply vacuum and proceed to "divide and conquer" until the leaking component(s) are isolated.

The plastic vacuum line I've seen packaged in rolls at AutoZone. It can be cut to length and shaped with a heat gun or possibly a hair drier. Rubber connectors can be had in generic form as well as vacuum solenoid switches.

Stopping here, because this is OT. But, begin another thread (if you haven't already) and we can help ya isolate the issue, if need be.

P.

[fletchusmc]

Haven't voted yet and not sure if I should add this to this thread but, what's the difference in the way the vacuum pump should run with key on engine off or key on engine on? The reason I ask is I just went out this morning, turned the key on engine cold. Pump runs and doesn't stop. Started the engine and let it run for close to 10 minutes and the pump never came on (but does come on when I disconnect the vacuum line). Turned off the engine and immediately turned the key back on and now the pump is on off on off on off constantly.

Drives great all the way up to the limiter. Just wondering what the difference in engine on and engine off when it comes to the vacuum.

1995, #297. Stock except Corsas.

[Dynomite]

Originally Posted by fletchusmc

Haven't voted yet and not sure if I should add this to this thread but, what's the difference in the way the vacuum pump should run with key on engine off or key on engine on? The reason I ask is I just went out this morning, turned the key on engine cold. Pump runs and doesn't stop. Started the engine and let it run for close to 10 minutes and the pump never came on (but does come on when I disconnect the vacuum line). Turned off the engine and immediately turned the key back on and now the pump is on off on off on off constantly.

Drives great all the way up to the limiter. Just wondering what the difference in engine on and engine off when it comes to the vacuum.

1995, #297. Stock except Corsas.

You will see Vacuum Check Valve #15 in Paul's post (this diagram is for a 1990 ZR-1) which lets Plenum Vacuum take over when engine is idling and Plenum Vacuum is high. Vacuum pump takes over when engine has wide open throttle and Plenum Vacuum is lower. Cruise Control and HVAC on passenger side of Plenum and Secondary Vacuum on Drivers side of Plenum.

Secondary Vacuum System for a 1990 ZR-1.


1. In your case you had High Plenum Vacuum at idle for 10 minutes (so vacuum pump remained off).
2. Pump came on when you disconnected vacuum line cutting off Plenum Vacuum to the pump.
3. With Key on and No Plenum Vacuum, Pump will cycle maintaining Secondary Vacuum as it is suppose to do. The more often the vacuum pump cycles the indication of more vacuum leaks present.
4. Pump cycling on and off every minute indicates minimal Vacuum Leaks under the Plenum. Pump cycling on and off every 5 seconds indicates Vacuum Leaks under the Plenum (Secondaries will remain operational as pump can keep up with the leaks if it cycles off no matter the cycle time).

When you first turned the key on and Vacuum Pump ran constantly......that might indicate the check valve #15 was stuck open or leaking and the pump could not build up vacuum because it was sucking air from the plenum.
Or....that might indicate with engine cold the vacuum leaks are unacceptable and with engine warmed up the Vacuum Leaks under the Plenum are significantly less (vacuum lines/connectors swell up closing down some vacuum leaks).

[5ABI VT]

Running out to the garage now to check mine.

[5ABI VT]

I unplugged from the passenger side where the tube goes into the plenum and capped it : 1:55 seconds before my fingers got tired. Plugged in.. 6 seconds and on for about about 1.

[fletchusmc]

Will have to do some digging around now. Later the same day I was finally able to get into an open enough stretch of road to open her up, ran all the way up to 7k like usual. I've got the FSM so obvious I need to do some homework on this part.