1990 ZR-1 secondary actuators binding?

[mmkkpro]

Hi guys, I pulled my plenum off yesterday to install new parts. So I'm checking secondary vacuum lines and all associated parts and I noticed the actuator arms that attach to the linkage seem to be off center. I know they look bad but they are not leaking down and seem to open properly, however upon releasing vacuum the only return about half way back to the closed position. Is this normal? Does engine assist the return to closed when it's running?
Thoughts on secondary delete? Thanks.

[A26B]

First part answer: The actuators were intentionally installed that way at Mercruiser. If you will notice in your first photo, the actuator centerline is aligned with the linkage pin. The arm has a 90deg bend to where it attaches at the center of actuator diaphragm. The pull is actually straight, but looks angled because of the bent arm. Engine assemblers thought it looked odd and experimented with rotating the actuator 180deg, but doing so actually did cause binding.

Second part answer. Actuator not returning to the the fully closed position is probably due to the linkage binding. The most probable cause is carbon on the SPT butterflies (valves).

Last part, regarding SPT delete. Tuning has progressed over the years, making deletion of the SPT system a recommended option.

[mmkkpro]

Thank you for the reply, greatly appreciated. 👍👍🏁

[Dynomite]

First part answer: The actuators were intentionally installed that way at Mercruiser. If you will notice in your first photo, the actuator centerline is aligned with the linkage pin. The arm has a 90deg bend to where it attaches at the center of actuator diaphragm. The pull is actually straight, but looks angled because of the bent arm. Engine assemblers thought it looked odd and experimented with rotating the actuator 180deg, but doing so actually did cause binding.

Second part answer. Actuator not returning to the the fully closed position is probably due to the linkage binding. The most probable cause is carbon on the SPT butterflies (valves).

Last part, regarding SPT delete. Tuning has progressed over the years, making deletion of the SPT system a recommended option.

i would say that a bit differently...........Most of us keep the very unique Full Power mode simply because that function is very reliable especially if you replace the vacuum lines and connectors for a mere $100 (the secondaires will last a very long time maintenance free). Not everyone can Delete the secondaries and I guess not everyone can replace the secondary vacuum lines either :p

Lets just say...........Having the Full Power switch functional on the dash is a BIG part of having the ZR-1 with the LT5. Oh ya....I have a 91 with deleted Secondaries and several other ZR-1s with secondaries upgraded with new vacuum lines and Full Power option completely fiunctional.

[A26B]

i would say that a bit differently...........
Lets just say...........Having the Full Power switch functional on the dash is a BIG part of having the ZR-1 with the LT5. Oh ya....I have a 91 with deleted Secondaries and several other ZR-1s with secondaries upgraded with new vacuum lines and Full Power option completely fiunctional.

I have both, a functional Valet Switch (key fits, turns to On & OFF position) AND deleted SPT. Just takes a little press with the right foot.:dancing

[mmkkpro]

Hello Dynomite, I do agree that the full power option is very important for this machine. My vacuum pump is dead, actuators are not leaking and do function, they don't look to swift. The vacuum lines are surprisingly in decent shape, so I priced the actuators at 65 bucks each, vacuum pump around 100 or so that's aftermarket the one im looking at is almost identical to the original one. I don't really want to delete the system. I reckon I will pull the IH, clean it and see if I can solve the sticking issue. I have gaskets on the way from Jerry's, got new injectors also. I appreciate and respect your guys opinions and knowledge, it really helps me decide, I thought I would have her running by now but I work a lot and I'm kinda on a budget, I have made a lot of progress though, hopefully she will be running in a couple of weeks, can't wait , thank you.

[Dynomite]

Hello Dynomite, I do agree that the full power option is very important for this machine. My vacuum pump is dead, actuators are not leaking and do function, they don't look to swift. The vacuum lines are surprisingly in decent shape, so I priced the actuators at 65 bucks each, vacuum pump around 100 or so that's aftermarket the one im looking at is almost identical to the original one. I don't really want to delete the system. I reckon I will pull the IH, clean it and see if I can solve the sticking issue. I have gaskets on the way from Jerry's, got new injectors also. I appreciate and respect your guys opinions and knowledge, it really helps me decide, I thought I would have her running by now but I work a lot and I'm kinda on a budget, I have made a lot of progress though, hopefully she will be running in a couple of weeks, can't wait , thank you.

You cannot go wrong with Jerrys gaskets.....the parts are perfect, super packaging, and the shipping is usually two/three days. Matter of fact I just broke the oil pressure sensor (gauge) changing out a Belt Tensioner Pulley (New one from jerry is Prolly in my mail box now) :handshak:

[mmkkpro]

Sweet, everyone says he is the man. 👍I think that's where I checked the price of actuators. I'm going to check the resistance on my wires and test the coils, need to clean the valley out its dry but some oil and debris, I don't even know how many miles is on it. The instrument cluster needed to be rebuilt so I sent it to Bryan at Batee.com, he did a fabulous job on it. Have not put it back in yet, guess I will see the mileage when I do. I have spent a lot of money and time on it so far and want to hear it run! The closer I get the more I want to rush but I gotta be cool a couple more weeks. I want it to be right before I even try, once I get the plenum back on I need to prime the oiling system, fill coolant and such. No telling what else I'm going to need like sensors and all. Just want to make sure the engine is OK before I spend too much more, but either way I'm committed to this build. I'm kinda jealous of you guys, yall got running ZR-1s. 👍👍😁

[Paul Workman]

Well, you just knew someone would come along and kick sand in the eyes of those speaking the praises of having the "switch".

After about the 2 or 3rd time under the plenum for SPT issues, OUT THEY CAME and good riddance!! Gone for good. Always in FULL ENGINE POWER mode and loving it! (And, with my 37.5mm porting, the SPTs wouldn't work anyway :jawdrop::razz:

Just sayin....:cheers:

[lfalzarano]

Who drives their Z in valet mode? Sinners repent!!!! Turn the key to full power and never change it!


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[Ccmano]

Have you tested the vacuum check valve? I have see at least two instances where the check valve failed causing the pump to run continuously subsequently burning out the pump. Replacing the check valve and pump restored the secondary system. I now always replace the check valve when going under the plenum for the first time. It’s cheap insurance on a cheap part that’s prone to failure.
H
:cheers:

[mmkkpro]

Hi Ccmano, no I have not checked but I will, how do you check it? Also does that vacuun solenoid give trouble? The pump looked like moisture got inside and killed it. I'm conflicted on keeping it or deleting it. I just know all them parts are ancient and will give trouble. I'm on a budget so got to figure out what to do. Pulling the plenum is not that bad so I may just recheck everything and reassemble her. I'm chomping at the bit to start her, I have spent a lot so far which is OK, just want to make sure the engine is in good shape which I guess really does not matter because at this point I'm committed to fix her no matter what.. I knew it needed a lot of TLC, things I didn't plan on like the sending unit for example. Everything I have done so far absolutely needed to be done just to start it. But it's all good, in excited to hear her run and drive her. Thanks.

[Ccmano]

Generally the check valve is tested with a good vacuum pump. If you turn the ignition on without starting the car and if the pump runs continuously, you pull the vacuum line on the left center (pass side) of the plenum and plug it with your finger causing the pump to stop running, you have a bad check valve.

With your burned out pump, apply vacuum with a hand pump to the line that goes from the burned out pump to the engine. You will likely see the vacuum does not hold. Now plug that same left center vacuum line. If vacuum now holds, bad check valve.

The vacuum solenoid, the vacuum reservoir and the actuators can all leak. Test them while your in there.

I have my secondaries deleted. Largely because I’m not interested in dealing with the drama of a 30yr old vacuum system. I suppose if your a purist you could say the secondaries are part of the cars appeal. Mine runs great, no regrets.

What’s cheaper to fix? In the short run fixing your system probably. At least until the next issue. Check valves are cheap, a few bucks, and a new vacuum pump about $100. Deleting the secondaries is simply the labor to pull the parts out, some plenum gaskets and a Haibeck Chip (about $250 last I looked). Probably best to simply wire the secondary throttle plates open. That way the next owner can take it back to stock if they want.

In the end it’s your call. Have fun.
H
:cheers:

[Dynomite]

I’m not interested in dealing with the drama of a 30yr old vacuum system.

Easily fixed and not expensive :cheers:

Just sold on Ebay three sets of new 1993-95 ZR-1 LT5 Corvette Secondary Actuator Vacuum Control Lines for $65 each including ALL connectors and Check Valves. The new 1993-95 ZR-1 LT5 Corvette Secondary Actuator Vacuum Control Lines can be easily modified to fit 90-92 ZR-1 LT5 :thumbsup:

Post 284 - New Secondary Port Throttle Vacuum System (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-15.html#post1596384583)

New 1993-95 ZR-1 LT5 Corvette Secondary .............Modified 1993-95 ZR-1 LT5 Corvette Secondary
Actuator Vacuum Control Lines................................Actuator Vacuum Control Lines for 90-92 ZR-1 LT5
https://cimg4.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x500/80-img_0873_bdb675bf531e6cbcf364979a3b4a21f0c7c5c7b3. jpghttps://cimg5.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/600x500/80-img_0878_4641cd899d09ea6411c7c98c72da5d59b7b0f848. jpeg

[mmkkpro]

Going to have to watch ebay closer, I did find a complete fuel sending unit assemble out of a 94z on ebay and bought it. I am going to fix the secondaries for now, ordered a new vacuum pump and have tested most all of the components, they seem to be working, may put in a new check valve as suggested above. Working on fuel injectors this morning kinda paranoid about the fuel lines at the back of the fuel rails. Ccmano wrote me a great step by step so going to follow his advice. Thank all you guys for your replies, very helpful and greatly appreciated👍👍🏁

[Ccmano]

While your in there re-torque the injector housing bolts. They have tendency to loosen and cause oil burning issues. If you find them very loose consider replacing the lower IH gaskets.
H
:cheers:

[mmkkpro]

Hi Ccmano, yea I can see where it's been leaking a little, dirty down there, no water though. I ended up taking the top clips off the injectors and pulled the fuel rail 10 injectors came out fairly easily but 6 were a little tough but I got em. While I wait for my new vacuum pump to arrive I'm going to clean the valley up a bit do the tighten bolts and check coils and wires. Looks like the original wires, thanks for everything, I appreciate the help no doubt.

[Ccmano]

The oil you see in the valley is more likely coming from the breather cover. (the square cover the vacuum solenoid and vacuum reservoir sit on) The cover bolts tend to loosen as well. Good to snug those down too.
H
:cheers:

[mmkkpro]

Got bolts tightened, injectors installed, vacuum pump installed and happy to report it runs and shuts off after a few seconds.
The secondary port vacuum solenoid is a question. With it still mounted and hoses off passenger side port holds vacuum, drivers side port does not hold a vacuum even if I plug the passenger side port or not makes no difference. Marc has posted a article about grounding the pink C17 wire at the ECM to test functionality. Should both ports on the solenoid hols vacuum, if so I guess it's bad and where could on be found? Still need to replace that check valve also just in case. I have read a vacuum solenoid off a Yukon will work with some bracket mods. Would anyone know what year Yukon or maybe a part number? Thanks, making progress!

[Ccmano]

Looking at the vacuum solenoid from the front (vacuum reservoir to the left) the left line is the vacuum supply line. When not energized this side of the circuit should hold vacuum. When energized the valve opens allowing vacuum to the right circuit. So if vacuum holds on the left not energized and releases vacuum to the right when energized, all is good.
H
:cheers:

[mmkkpro]

Thanks Ccmano, I spoke to Marc by email and he said he would get me a part# of the new type he uses, may just go ahead and change it out, chances are I will be back under the plenum at some point soon, not sure if ac compressor or alternator are good either.
Check out the old injectors, from the looks of them there is no way the secondary injectors were working by all the build up on them. The primaries don't look too bad relatively clean. That kind of build up on the secondary injectors would not happen by just sitting would they? Based on their condition no way they could have been working. I took that solenoid off and I could blow right through the right port, the air came out of the back of the assembly and it does not have a conical filter on it either. Thanks for all the help.

[Ccmano]

Thanks Ccmano, I spoke to Marc by email and he said he would get me a part# of the new type he uses, may just go ahead and change it out, chances are I will be back under the plenum at some point soon, not sure if ac compressor or alternator are good either.
Check out the old injectors, from the looks of them there is no way the secondary injectors were working by all the build up on them. The primaries don't look too bad relatively clean. That kind of build up on the secondary injectors would not happen by just sitting would they? Based on their condition no way they could have been working. I took that solenoid off and I could blow right through the right port, the air came out of the back of the assembly and it does not have a conical filter on it either. Thanks for all the help.

Those are the original injectors. If they are not bad now they will be at some point in the near future. 90’ -92’ injectors were not compatible with the ethanol now used in fuel. It corrodes the electronics. I would replace them all now. The secondaries look like that because of lack of use. Back in the day owners only occasionally turned the “power key” on to run on full power. As we now know the result was carbon buildup on the respective intake valves and injectors. Today we recommend the secondaries be run all the time to allow the fuel to keep those areas clean and properly working.

Marc is todays ultimate source of LT5 knowledge, go with what he tells you.
H
:cheers: