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Topic: Hard Start Cold

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


Hard Start Cold

Posted: 11/16/05 3:52pm Message 1 of 14
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Rockland, MA - USA
Joined: 1/30/2003
Posts: 584
Vette(s): 76, L48, 4spd & 09, LS3, 6spd

My Vette (76 - L48, 4spd, Stock, Qjet) always needs about 10-12 pumps of the pedal to get started, after sitting more than a day or two.

Is this just the nature of the beast or is a carb rebuild in it's future? Once started, it runs great, choke works as normal and then will idle smooth, etc. Warm starts are not a problem.

We seem to be getting closer to the "off season" every day and was thinking "might as well" add this to the list.

Thanks

 




 

 

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Hard Start Cold

Posted: 11/16/05 5:53pm Message 2 of 14
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WEST SENECA, NY - USA
Joined: 12/3/2001
Posts: 2379
Vette(s): 1981 Blue Ice Met. w/pearl ghost flames TKO500 5speed. LS1 Swap 3.45 Dana 44.

Sounds like a common Q-Jet problem. There are lead plugs at the bottom of the fuel bowl, they have a tendency of leaking while sitting for a day or so. If you are going to rebuild your Q-jet, use a 2 part epoxy and coat the lead plugs. This helps with the leak down problem.

Plus it seems that your accelerator pump may be a little worn since you have to pump the heck out of it.

Before you go rebuilding you carb, check the primary (front) throttle shaft for excessive play. Grasp the throttle linkage and try to move it front to back/ up and down. If there is slop in there, the throttle shaft is worn, this will cause a vacuum leak which is common to Q-Jets. This problem requires some drilling and bushings installed to make a rebuild work properly. There are kits available for that problem.

Let us know what you find

Sarge





GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975




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Hard Start Cold

Posted: 11/16/05 7:59pm Message 3 of 14
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
Good info from Sarge.  But don't overlook the simple.  Is the choke plate closing when cold?


Hard Start Cold

Posted: 11/17/05 10:09am Message 4 of 14
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Rockland, MA - USA
Joined: 1/30/2003
Posts: 584
Vette(s): 76, L48, 4spd & 09, LS3, 6spd

Thanks Sarge and Ken for your responses. I have a carb book by Doug Roe and saw a picture of the plugs you are referring to.

Does that fuel leak into the throtle body or out through the gasket? I have never seen what appears to be a leak around the gasket.

I'm still trying to figure out how a carb is supposed to work. With Doug Roe's book, and the the write up that Ken did - I seem to comprehend a bit more each time I go through it, but those first two or three attempts were very discouraging to say the least. 

I still plan to rebuild it myself, but I need to get my confidence level up just a bit more. 

Thanks again -

 




 

 

Hard Start Cold

Posted: 11/17/05 1:44pm Message 5 of 14
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
Something else to consider...besides what has already been said regarding the carburetor, gasoline today is blended primarily for fuel injected cars and evaporates quicker than the gas available when our cars were built, resulting in the need to crank the engine and pump the pedal more to get fuel into the carb to begin with. If your carb has any problems, this just aggravates the situation.


Hard Start Cold

Posted: 11/17/05 6:32pm Message 6 of 14
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
Typically the fuel that leaks drops down on the throttle and into the intake.  It slowly evaporates from there leaving no trace.  Due to the air cleaner you normally won't even notice a smell.


Hard Start Cold

Posted: 5/4/21 8:53am Message 7 of 14
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Canada
Joined: 7/16/2007
Posts: 15
Vette(s): 1976 Stingray, blue, 4 spd., one owner (me)

Yes, I've tried just about everything I can regarding the hard starting of my '76, including the 'well plugs'.

I've decided it is the loss of the anti-evaporation additive in modern fuels that is causing it. 

Oh well, just keep cranking.




Re: Hard Start Cold

Posted: 5/4/21 10:29am Message 8 of 14
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Scottsdale, AZ - USA
Joined: 5/23/2007
Posts: 617
Vette(s): 1981 Corvette Two-Tone Claret color, 4 spd, C7 Vert

New fuel pump in recent history?




      Only 34 years together

Re: Hard Start Cold

Posted: 5/4/21 11:12am Message 9 of 14
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Canada
Joined: 7/16/2007
Posts: 15
Vette(s): 1976 Stingray, blue, 4 spd., one owner (me)

Alas yes, last year, didn't make any difference.




Re: Hard Start Cold

Posted: 5/5/21 8:26am Message 10 of 14
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Grapevine, TX - USA
Joined: 8/26/2006
Posts: 1525
Vette(s): 1972 LT-1 convertible with factory air. 2017 Black Rose Grand Sport convertible.
Gunslinger said: Something else to consider...besides what has already been said regarding the carburetor, gasoline today is blended primarily for fuel injected cars and evaporates quicker than the gas available when our cars were built, resulting in the need to crank the engine and pump the pedal more to get fuel into the carb to begin with. If your carb has any problems, this just aggravates the situation.


It's not blended "for fuel injected" cars.  It's blended for the EPA and their stupid regs.

My Holley carb doesn't have this problem. Starts right up after sitting for a month.




   

in Forum: C3 Fuel, Emission Control, and Exhaust Systems


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