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Discussion Starter · #1 ·
From Another Forum:

Perfect time for a carburetor choke Issue especially since I live in Los Angeles and it's been 100+ degrees. When starting my engine after sitting overnight I press the accelerator one time and the choke butterfly closes. I turn the key and the engine roars to life and the RPM's indicate that the choke is functioning as it supposed to for about 2 seconds and then the RPM'S drop and the engine sounds as if it is starving for gas. I have a poor idle almost stalling for about minute then the RPM'S sneak back up to the original fast idle speed and I can drive off. Within a short time the choke comes off and I can cruise around happily the rest of the day.

Could it be fuel is leaking from the bowls overnight and during that first start of the day it takes the fuel pump that extra time to refill them. Where would the gas go? I see no evidence of gas leaking from the carb plumbing. Any trouble shooting suggestions would be appreciated.


This is why I recently installed a push button fuel bowl priming switch. I found after a hot shut down the fuel was boiling and evaporating so much my fuel bowls were nearly empty the next morning. As my late model Street Avenger has sight glasses I could see the fuel levels were way below the sight glasses. My front bowl still had enough fuel for the accelerator pump to work and start my engine but not enough fuel to keep it running long enough for the pump to fill the bowls. Ever since I installed the push button switch my choke and fast idle operation has been flawless.

I installed my push button switch on the right side of my parking brake console:
 

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From Another Forum:

Perfect time for a carburetor choke Issue especially since I live in Los Angeles and it's been 100+ degrees. When starting my engine after sitting overnight I press the accelerator one time and the choke butterfly closes. I turn the key and the engine roars to life and the RPM's indicate that the choke is functioning as it supposed to for about 2 seconds and then the RPM'S drop and the engine sounds as if it is starving for gas. I have a poor idle almost stalling for about minute then the RPM'S sneak back up to the original fast idle speed and I can drive off. Within a short time the choke comes off and I can cruise around happily the rest of the day.

Could it be fuel is leaking from the bowls overnight and during that first start of the day it takes the fuel pump that extra time to refill them. Where would the gas go? I see no evidence of gas leaking from the carb plumbing. Any trouble shooting suggestions would be appreciated.


This is why I recently installed a push button fuel bowl priming switch. I found after a hot shut down the fuel was boiling and evaporating so much my fuel bowls were nearly empty the next morning. As my late model Street Avenger has sight glasses I could see the fuel levels were way below the sight glasses. My front bowl still had enough fuel for the accelerator pump to work and start my engine but not enough fuel to keep it running long enough for the pump to fill the bowls. Ever since I installed the push button switch my choke and fast idle operation has been flawless.

I installed my push button switch on the right side of my parking brake console:
The hardest thing to do is "diagnose over the phone" but I would want to know if needle valve(s) are seating. As to the cold start the choke is suposed to be involved with the idle alot longer than a few seconds. I would suspect the choke setting.
 

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The hardest thing to do is "diagnose over the phone" but I would want to know if needle valve(s) are seating. As to the cold start the choke is suposed to be involved with the idle alot longer than a few seconds. I would suspect the choke setting.
CVAL, welcome to our tiny C3 forum that is barely existing. Let me explain what happens after a HOT shut down of a carbureted engine. After the HOT shut down heat in the block, heads, and intake rises which makes the fuel in the carburetor so hot it begins to boil and then evaporate. I have actually seen fuel gushing out of the vent tubes of my Holley about 3 minutes after shutting my 454" off.

Within an hour the fuel bowls are nearly empty so when an attempt is made to re-start the engine only the accelerator pump functions. The engine will start but then quickly die because the fuel bowls don't have enough fuel in them to keep the engine running.

So it takes a good 5 to 7 seconds of cranking to refill the fuel bowls enough for the engine to start but it runs real rough until they get completely filled. It's just the way things are with our modern gasoline.
 

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Perhaps I should tell you alittle of myself. I was raised next door to my father's repair business, Val's Auto and Truck Repair, I started wiping tools before I was old enough for Kindergarden. I reached first class at the age of 17, not by Father but when he threw me out " you don't know how good you've got it" but by Quaker City Dodge in center city Philly. Eventually he somehow talked me into buying the business and it was quite successful up until the day I sold it.
I'm not bragging when I say there's nothing on your vetted I can't fix, but diagnosing over the phone is one of the hardest thing this NIASE and ASE certified Master Tech has ever tried to do. BUT Jjust for shits and giggles you might look down the throat of that carb right after hot shutdown and see if it's dripping, just a thought. BTW, my nickname
WAS Corvette Bob I know them, owned them and sold them, anyway good luck with your toy. CVal
 

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Discussion Starter · #5 ·
Perhaps I should tell you alittle of myself. I was raised next door to my father's repair business, Val's Auto and Truck Repair, I started wiping tools before I was old enough for Kindergarden. I reached first class at the age of 17, not by Father but when he threw me out " you don't know how good you've got it" but by Quaker City Dodge in center city Philly. Eventually he somehow talked me into buying the business and it was quite successful up until the day I sold it.
I'm not bragging when I say there's nothing on your vetted I can't fix, but diagnosing over the phone is one of the hardest thing this NIASE and ASE certified Master Tech has ever tried to do. BUT Jjust for shits and giggles you might look down the throat of that carb right after hot shutdown and see if it's dripping, just a thought. BTW, my nickname
WAS Corvette Bob I know them, owned them and sold them, anyway good luck with your toy. CVal
After a HOT shut down you'll see gas gushing out. Out of the bowl vents and out of the boosters and it'll continue to gush out until the bowls are nearly empty. I first heard the gas boiling then saw gas blowing out of my bowl vents 3" high one 100 degree afternoon about 3 to 4 minutes after shutting it off. The gasoline in "the old days" didn't boil and evaporate like it does now.

I have known several ASE certified mechanics who after 50 years still didn't know what they were doing.
 

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Well wearing the badge doesn't make you an actual accomplished tech but it shows you care enough to earn it. I couldn't care less if you don't respect my expertise but you obviously can't fix it, maybe someone with over 50 years experience ( I'm 74) has seen that more than once and supported a family with the ability to repair the problem and make a profit might. In any event I didn't join to argue and I won't respond to you again.
 
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