Secondary Vacumm Pump question???

[Schrade]

Some 2nd vac pump breakdown / diags snappics here, starting post #346 http://www.zr1.net/forum/showthread.php?t=21439&page=9

[Dynomite]

Originally Posted by efnfast

I'm no expert here, but I don't think the secondaries will open at all without the vacuum pump. And if it's revving to 7K, we can assume the secondaries aren't there?

You get vacuum from two sources for secondary operation (Vacuum pump and Plenum). There is a check valve that opens when plenum vacuum takes over. When the Vacuum pump is working that check valve is closed such that the Vacuum pump does not start evacuating the Plenum.

Secondary port vacuum diagnosis TIPS

[Roadster]

Originally Posted by KILLSHOTS

If you can redline the car with the pump disconnected, then your secondaries are removed. If they were intact, you'd have a hard time revving past 5000. Just turned off my key and confirmed that about an hour ago.

Hey, Chris, thanks for the confirmation on that.....
Still in the learning process with all of this, had no idea or reason to believe that the secondaries could or would be eliminated on my 94. And yes as stated before it does make sense that if the secondaries were in tact and the pump disconnected that the engine would not run as good as it does.
Now I need to find out who removed them and when.....hmmmmm!!!

[Dynomite]

Originally Posted by Roadster

Hey, Chris, thanks for the confirmation on that.....
Still in the learning process with all of this, had no idea or reason to believe that the secondaries could or would be eliminated on my 94. And yes as stated before it does make sense that if the secondaries were in tact and the pump disconnected that the engine would not run as good as it does.
Now I need to find out who removed them and when.....hmmmmm!!!

No.....you need to find out who clobbered up the Secondary removal and remove the plenum and do it right
Also.....you might have a modified chip to account for secondary removal......

Originally Posted by KILLSHOTS

If you can redline the car with the pump disconnected, then your secondaries are removed. If they were intact, you'd have a hard time revving past 5000. Just turned off my key and confirmed that about an hour ago.

It appears that you do not have functional secondaries....and possibly someone removed the secondary function without removing the whole secondary system (tying the secondaries open for example and leaving all the vacuum lines in place).

[Roadster]

Originally Posted by Dynomite

No.....you need to find out who clobbered up the Secondary removal and remove the plenum and do it right
Also.....you might have a modified chip to account for secondary removal......

I kow that some day I will have to pull the plenum and yes, do it right....

If you might remember I had the Tim Holland Chip in there from the early GM engineering days of ownership. I then ordered a chip from Marc, and of course at the time had no idea that my secondaries might be eliminated. The main reason I went with the chip was to get the fans to come on & off at the lower temps. So Marc's chip that is in there now, does not have any provisions for secondary removal. And I know I keep repeating myself, but it runs great.....
I have noticed some oil around a Torx screw or two, especially around number 1 cylinder, so I need to snug those down.
Actually I need to retire to keep up with my vehicles, but I am a few years away from that. I'll just wait until the colder weather before I do a pull, did receive my DVD from Marc and with your links and people who have done it already, hopefully it won't be complicated once I get into it.
And being in the area of the WAZOO gang, maybe I can hook-up with them sometime in the future whenever they do a Plenum pull day.......

[Roadster]

Originally Posted by Schrade

Some 2nd vac pump breakdown / diags snappics here, starting post #346 http://www.zr1.net/forum/showthread.php?t=21439&page=9

Thanks for the pic and link, some serious reading there for sure, it is bookmarked for future use......

[Roadster]

Originally Posted by KILLSHOTS

If you can redline the car with the pump disconnected, then your secondaries are removed. If they were intact, you'd have a hard time revving past 5000. Just turned off my key and confirmed that about an hour ago.

Ok Chris, you got me in the mood, did my second complete WOT minutes ago (deserted road, no one around) out of 1st gear on a slight roll, looks like I shifted around 7200 r's just slightly above the 7k marking on the tach. Just unbelievable, I could do that all day long. Not a hiccup, just pure LT5 engine power....Coolant Temp @ 204* Oil Temp @ 208* fully warmed up motor....vacuum pump disconnected as usual, apparently no secondaries to be found......

[KILLSHOTS]

Originally Posted by Roadster

Ok Chris, you got me in the mood, did my second complete WOT minutes ago (deserted road, no one around) out of 1st gear on a slight roll, looks like I shifted around 7200 r's just slightly above the 7k marking on the tach. Just unbelievable, I could do that all day long. Not a hiccup, just pure LT5 engine power....Coolant Temp @ 204* Oil Temp @ 208* fully warmed up motor....vacuum pump disconnected as usual, apparently no secondaries to be found......

There's the Permagrin!

[Roadster]

Originally Posted by KILLSHOTS

There's the Permagrin!

You got that right......

[weldbead]

Originally Posted by Dynomite

No.....you need to find out who clobbered up the Secondary removal and remove the plenum and do it right
Also.....you might have a modified chip to account for secondary removal......



It appears that you do not have functional secondaries....and possibly someone removed the secondary function without removing the whole secondary system (tying the secondaries open for example and leaving all the vacuum lines in place).

what would be the down side of physically tying the butterlies open but leaving the the ailing vacuum system alone?