help please for a new member

[Z51JEFF]

As stated the new pump is form a G.M. Kodiak and is the same part as 91-95.The only difference is the plug for the 90.All this for less than $140.I too think the problem is under the plenum.I believe the pump will cycle,stop for a an amount of time and cycle and so on.

More than likely you don't have a problem with your pump and the source will be traced to under your plenum, but I would buy one at that price anyway since your pump has been running continuous at times and you don't know the history of it. Someone has been buying up even these Kodiac pumps and selling them at premium on Ebay. These parts are getting more difficult and expensive to purchase and if I knew 6 years ago how hard it would be to find some parts and how high the prices would go I would have stock piled and went into ZR-1 parts business myself. Seal every vacuum connection under there with silicone or other sealant that is not permanent and zip tie for extra insurance; that is all that I had to do to mine too.

[Dynomite]

Originally Posted by Z51JEFF

As stated the new pump is form a G.M. Kodiak and is the same part as 91-95.The only difference is the plug for the 90.All this for less than $140.I too think the problem is under the plenum.I believe the pump will cycle,stop for a an amount of time and cycle and so on.

I just tested my old vacuum pump as well as a new vacuum pump and neither vacuum pump recycled when vacuum was held for about a minute using a long vacuum line attached but blocked off. So.....your vacuum pump should hold a vacuum longer than 3 seconds I would think if in fact you had it blocked completely off with your finger. I got different results several times because I did not block off the vacuum line good enough with my finger.

I think you also have leaks beyond the vacuum pump under or on the way to the plenum.

Originally Posted by HAWAIIZR-1

I found most helpful with the same vacuum issue when I got my 90:

http://www.corvetteactioncenter.com/...cuum+Diagnosis

The web site provided by HAWAIIZR-1 is about the best to diagnose a vacuum leak

[Z51JEFF]

Originally Posted by Dynomite

I just tested my old vacuum pump as well as a new vacuum pump and neither vacuum pump recycled when vacuum was held for about a minute using a long vacuum line attached but blocked off. So.....your vacuum pump should hold a vacuum longer than 3 seconds I would think if in fact you had it blocked completely off with your finger. I got different results several times because I did not block off the vacuum line good enough with my finger.

I think you also have leaks beyond the vacuum pump under or on the way to the plenum.

If I block the pump itself it shuts off,when connected to the system,key on the pump will come on,pull vacuum,go off for 10 seconds and them come on for one second then off and 10 seconds so on.

[xlr8nflorida]

Would this connector work its 50% off the other price and that includes shipping.

http://cgi.ebay.com/ebaymotors/Oil-l...25159008r11115

[BOB HDZ]

MARK HAIBECK of http://zr1specialist.com/HAT%20Web/products%20index.htm can reprogram your eprom so you can remove the air pump and the secondary!!! I had it done works great!!!

[tomtom72]

Originally Posted by richard sanderson

Thanks guys, My problem is that with everything connected up, the pump runs continuously, and with the pump disconnected and blocked off at the arrow in the above photo, the pump runs intermittently. So that tells us there is something wrong with the pump (can it be repaired?), and something wrong under the plenum, I guess. Maybe that is why the engine seem so strong although it has already done 125000! Nobody has managed to stress it for quite a long time! I live in hope. cheers Dick

Rich, What does the pump do if the motor is running at idle speed? Does it behave the same as with the KOEO test? If yes, then do the vacuum test on the other end of the connection @ the red arrow in Mike's picture ( thanks Mike! ), to see if the under plenum stuff is okay. I can't see the pump having that big of a leak if it is mostly off when the motor is at idle speed. It would have overheated the motor and blew the fuse or melted the connector slightly. I think something under the plenum is the real source of this issue. As you can see from Craig's link and Mike's picture there are plenty of candidates!

You could try to add a check valve from the outside ( to test the one under the plenum near the tank ) and then redo the vacuum test. Heck if that makes the system under the plenum hold vacuum, then you're done as the OE check valve is N/G. I do believe for this trick/test using an additional check valve you need to connect it to the left side vacuum hose that is at the mid point on the left side of the plenum. That, intake manifold vacuum, is the real vacuum source for the secondary system. The connector is located between the front & rear sets of runners off of the plenum. Just make sure the connections are sealing for the test. If the system still will not hold vacuum then the tank or maybe the solenoid or maybe any of the connectors and maybe even the secondary pull-off canisters could be the source of the leak(s). If after the temp check valve test fails you will have to pull the plenum to investigate further the source. Sorry, I don't know of any way to test that stuff under there beyond what I have listed. Some one else may have some knowledge to share on this as I'm no expert on an LT5!

On a some what related subject, if you want to take your pump apart and recondition it let me know. The only special talent needed to work on the pump is patience and soldering ability. It's a simple electric motor and a plastic press together case. You just pry the top of the pump off to get at the guts. If you look closely from above you can see the seam. The only thing is it was so long ago that I can't remember much, senility I'm sure. It's a simple machine and once opened up you just really see what the issues could be, mine was rust! However, if yours behaves as you say I would not worry about the pump.


Tom

[ZZZZZR1]

Originally Posted by richard sanderson

Hi Everyone, I would like some advice if that would be possible. Especially as I live in the south of Spain, so I am obliged to do all my own mechanics - nobody round here has even heard of a ZR-1! (Mind you, if someone feels insulted by this comment, please get in touch and I will give a grovelling apology, and be very grateful for any help they might be able offer). Anyway, the first problem I had to fix was that the Src light had been taken out, so although the suspension was naz, no codes were set. But after having to pull the dic and rearrange the lights in the proper place, I now have got that bit sorted and can get on with fixing the ride. Next the secondary vacuum doesn't seem to behave correctly. When the ignition is on but the engine is not running, the pump runs continuously. If I unplug the pipe from the pump, and block it off with my finger, it runs in little bursts, say 1 second on then 3 second off. I assume something is wrong under the plenum. So I have printed out the Big Country Corvettes instuction sheet, and am preparing to assemble all the bits I will need for a plenum pull. Item 5 in the removal procedure says remove the vacuum hose with a flat blade screwdriver. But idly fiddling around with things while going over these instructions on the car, I gave a very slight tug on this pipe, it came off the rubber tubing that goes into the plenum. Should this rubber tube be removed from the plenum, or could this be the cause of my leak anyway? Also, looking through other posts, I am unsure whether this secondary vacuum system is actually necessary to get into full power. Can full power mode be acheived without this part of the system working? I dont want to tie the secondaries open. I am too much of a purist to want to cheat on something like that. Any comments welcome! Richard - 1990 #231

Richard,

have you spoken to our Spainish ZR-1 there? Pete / Fernando / Pedro / Salvador?

I'll email them a link and get them to respond. Pete works on Z's there and they get together OFTEN there as well.



David

[EuroPete]

Originally Posted by ZZZZZR1

Richard,

have you spoken to our Spainish ZR-1 there? Pete / Fernando / Pedro / Salvador?

I'll email them a link and get them to respond. Pete works on Z's there and they get together OFTEN there as well.



David

Hello! Thanks for the e-mail notice Dave, I just saw it and I rushed to the forum immediately.

Richard, although I live in Madrid I have a very close contact with other ZR-1 owners in Spain so PM me any time and we'll do our best to assist you. Personally I'm not the best well read person about LT5 tech issues but my friends Ramon and Toni will surely help you out. Nobody in our country knows more than them about these cars, trust me.

Talk to you soon.