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Topic: Weird startup when warm

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Weird startup when warm

Posted: 5/9/07 10:49am Message 1 of 9
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Eagleville, PA - USA
Joined: 11/1/2001
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Vette(s): Used to own a 1979 Corvette now owned by JB79
When I first start my Vette, it seems the choke isn't working because there never really seems to be a high idle.

After running it for awhile, like a few mile trip to a store, then I leave it off for 10 or 20 minutes, then get back in to start it up, if I do not constantly pump the gas while turning the key, then keep giving it some juice for the first 10 seconds, it will not start or stall out.

Any ideas what is going on here?

The carb was rebuilt a couple of years ago by that carb guy in Bowling Green that spoke at C3X.  Is it time for a new carb or what?

Thanks!





-Adam Wartell
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Founder: C3 Vette Registry 
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My first Vette, now owned by JB79:

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Weird startup when warm

Posted: 5/9/07 3:23pm Message 2 of 9
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Australia
Joined: 5/6/2004
Posts: 535
Vette(s): 71 Coupe Black on Black
Sounds like a temperature dependant vacuum leak somewhere Adam.  I've seen this happen from time to time.  When the car is cold, the parts causing the leak close up but once the engine heats up it leaks.  Could be a hose, gasket or even a valve in the carb somewhere.
 
Are you running a quadrajunk or a Holley?



Weird startup when warm

Posted: 5/9/07 6:18pm Message 3 of 9
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Eagleville, PA - USA
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Vette(s): Used to own a 1979 Corvette now owned by JB79
It's a quadrajet.


-Adam Wartell
NCM Lifetime Member #1222
Founder: C3 Vette Registry 
C4 Vette Registry, C6 Vette Registry

My first Vette, now owned by JB79:

Weird startup when warm

Posted: 5/9/07 7:36pm Message 4 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Adam, is it hard to start like this when it is cold, or only after running for a while?
I have seen Q-pukes blow/burn out the base gaskets, and be hard to start, but that usually also makes the idle high, and very erratic. You nay have a swollen float in the carb, and a bad/worn out accelerator pump. If the float level sticks low, and the pump is worn to the point of not supplying a full shot-o-fuel, it can cause this exact problem, but it would be the same cold or hot.
Have you put any additives in the fuel while it was stored?
Not having a fast idle could simply be an adjustment to the idle screw for the choke.



Joel Adams
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Weird startup when warm

Posted: 5/10/07 3:29pm Message 5 of 9
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Australia
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Vette(s): 71 Coupe Black on Black
I'm with Joel on this one.  If you have access to a Holley 600, you may be able to throw it on and see if there is any difference.  If there is you can make a decision to keep the Holley (I've found they are a lot easier to set up and keep in good condition) or get the Quadrapuke rebuilt professionally.  The Quads are great carbs if looked after properly and set up right.  A Holley on the other hand is so much easier to work on and set up correctly.
 
Others may tell you different but it's just my opinion.
 
Something I forgot to ask, does your '79 have a EGR valve on it?  If so, the valve may be playing up.
Chips582007-05-10 15:30:45


Weird startup when warm

Posted: 5/10/07 3:35pm Message 6 of 9
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As mentioned above, I already had it rebuilt professional two years ago.  That is why I'm thinking it is time to toss it and put something else in it's place. 

I think it has an EGR valve.  What does it look like?  What can I do to clear it out/clean it up?

Thanks!



-Adam Wartell
NCM Lifetime Member #1222
Founder: C3 Vette Registry 
C4 Vette Registry, C6 Vette Registry

My first Vette, now owned by JB79:

Weird startup when warm

Posted: 5/10/07 6:35pm Message 7 of 9
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Pass side of engine...

                                      


I've never had great luck in cleaning them, but sometimes, it does work. If it is carboned up a lot, enough to hold it open, you can open it with your fingers, while the engine is running, and possibly blow whatever is holding it open out. At the same time, you could also blow whatever is holding it open straight down into the cylinder...not really a gud thing.
It's best to remove it, and clean it with some good spray carb cleaner, while working the diaphragm up & down with your fingers....or just replace it if it is nasty. Adams' Apple2007-05-10 18:39:51


Joel Adams
C3VR Lifetime Member #56    

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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Weird startup when warm

Posted: 5/11/07 12:43pm Message 8 of 9
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San Pedro, CA - USA
Joined: 5/26/2005
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Vette(s): 1971, LT-1, T-top, 4-speed (M21), Mulsanne Blue, 3.70 rear, mostly original (sidepipes). 2006, Daytona Sunset Orange Coupe.
I've had this problem on my Vette (Holly), and all it usually needs is a mixture tweak, and idle adjustment.


Weird startup when warm

Posted: 5/11/07 3:25pm Message 9 of 9
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Australia
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Vette(s): 71 Coupe Black on Black
I had a similar problem with a Ford I once owned.  Yeah I know it's a four letter word but the EGR valve played up and all I did was get rid of it and plug up the hoses and put a plate over the hole left by the valve.  I just didn't tell the inspectors that it had one originally.  Way too many hoses in a Ford so he was always confused so no problems.


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