Vacuum pump not coming on?

[QB93Z]

Good job finding the vacuum leak.

Here is a picture of the major parts of the Positive Crankcase Ventilation system:



Are you missing any of these pieces? On some cars, the rubber gets soft and these pieces don't stay connected. You may need to put some zip ties around the parts to hold them.

Jim

[1963korvette]

Couldn't get pic of where they connect. but the left side comes to the back of engine and t's off with one end going down on to the valve and the other end is the loose one. The right side goes down under to who knows where couldn't see what it connects to. Sorry can't give better description.

[1963korvette]

Now that I think about it. I don't believe that that top piece in photo is on the motor does that connect left side to both valves? I have a plastic T.

[QB93Z]

The two metal PCV valves plug into the two sockets in the long rubber hose. The smaller rubber piece plugs on to the top of the two PCV valves. The whole assembly is installed behind the plenum. The longer rubber piece connects to the left and right sides of the engine through metal tubing and then a right angle rubber fitting into the Injector Housings, (the left hand arrow in your pic.)

The top rubber piece connects to metal tubing (the right arrow in your pic) that runs along the driver's side of the plenum and connects to a rubber fitting under the front of the plenum.

You will meed four small hose clamps to securely connect the four openings for the long, lower rubber piece (one on each end, one on each PCV valve).

Good Luck.

Jim

[1963korvette]

Ok. Jury rigged PVC connections til I order new rubber parts. Idle went down to 1400. Looked for other air leaks could not hear or see any. Went for ride and it acted like it was going to stall out. Ran very rough and sounds like a diesel engine. The battery doesn't seem to hold a charge, going to replace next week. Any thoughs.

Rich

[tccrab]

Rich:

ZR1's are very fussy about battery strength.
If the battery drops much below 12v all kinds of gremlins can jump out and bite you.
Getting a new battery is a must if yours is having charging issues.

Your idle is getting better, sounds like you've still got vacuum leaks.
It should normally idle at 850.
On my '90 I chased a vacuum leak for ages that was causing idle issues.
Turned out to be a vacuum connector just behind and under the throttle cables. It's hard to mess with because it's tucked underneath there and if it's not exactly right the damn thing leaks like a sieve.
It's a '90 model year only connector, GM realized it was not a brilliant design so they changed it in '91.
I was able to buy a new one from JeffVette (a.k.a. Jeff Flint) here on the forum. He has the worlds only supply of spares. After replacing mine, I decided if it ever gave me problems again that I'd re-engineer the connection and get rid of the #@!#$%%ing thing.

Idle aside, the running rough could mean many things. Fuel injectors, coils, wires, plugs all come to mind.

I'd highly recommend that someone familiar with these engines pay you a visit for a little diagnosis assistance.
Nothing is cheap for these cars, and I'd hate for you to just throw buckets of money at the car unless you had to.

Do you have a FSM (factory service manual) for this car?
It's an absolute necessity if you're going to work on this car yourself.
If not, here's a link:
http://www.helminc.com/helm/product2...X5WR6BV30U2TQ1

TomC
"Crabs"

[tomtom72]

Rich,

Not to beat a dead horse, but did you locate the MAP sensor vacuum line at the rear of the plenum and check to see it is still on the plenum port and not filled with oil?

Sorry, not trying to be a wise guy... It is important that the MAP is getting a vacuum signal. That hose is the first casualty if the motor backfires at start up. It can also get loose with age and come off very easily if you were poking around back there...like working on the bottom PCV hose.

I'll PM you my digits just in case you need moral support!


Tom

[1963korvette]

No I did not locate the map sensor yet. I did not really look for it yet. I was so happy just to find the PVC laek I forgot to look for that. I will look tonight.
Thanks

[QB93Z]

Just for reference, here is a picture showing the location of the MAP Sensor. This is a 1993 LT5, and there are some differences from your 1990, but the MAP is the same.



If the MAP hose is softened, it will collapse under high vacuum in the plenum. High vacuum occurs at idle and low throttle operation.

Good luck,

Jim

Originally Posted by QB93Z

Just for reference, here is a picture showing the location of the MAP Sensor and hose. This is a 1993 LT5, and there are some differences from your 1990, but the MAP is the same.

Jim, the hose you are pointing is the Fuel Pressure Regulator Hose.

Map sensor hose can't be seen from the top or side. Need to reach down and feel it.