1990 ZR-1 secondary actuators binding?

[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

[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

[Dynomite]

Originally Posted by Ccmano

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

Easily fixed and not expensive

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

Post 284 - New Secondary Port Throttle Vacuum System

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

[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

[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

[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