Quadrajet Starting Questions...

MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
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Des Moines, Iowa
#1
With an overnight cold engine, I have to pump it once to the floor to set the choke so it will start. Or I sit there and crank it for 30 seconds like an ***hole. It then idles up to about 1400, down to 1000, then settles at 12-300. Why? I can kick it off to curb idle, but why does it idle up and down so much in the first 10 seconds of starting? Choke pulloff not adjusted right? Cold engines need more fuel and less air than a warm one, so i think the pulloff is opening the choke too far and causing the weird rpm drop... what say you guys?

Also, I think the factory style air cleaner is making my carb percolate. It takes about 15 seconds of cranking to get it to start after it's been running at temp and then shut off. I can restart it immediately and upto about the 3 minute mark, then it takes some cranking. The starter doesn't drag, I look down the barrels and it's wet. It didn't do this with my other qjet (same model) with a 14x2 chrome dealy. Shame, I really do like the look of the factory air cleaner. I guess it's either live with it, or change back.

***EDIT: Yes I have since installed the breather hose and crank case filter into the air cleaner. It did this hot starting nonsense before and after the hose, with this air cleaner.***
 

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MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
113
Des Moines, Iowa
#2
And in my air cleaner, there is a thing with two nipples on it with an A/C written on it. It's some kind of valve/plunger thing. What's it for? Part of the AC system of the car it's from?
 
RegalBegal

RegalBegal

G-Body Guru
Jul 10, 2009
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Lebanon, New Hampshire
#3
The surging in startup could be many things. A vacuum leak, worn throttle shafts etc. you'll have to do some hunting. check this link here. The hard starting after sitting could be caused by the plug wells in the carb leaking down. This is a common Qjet problem. My guess is thats why when you look down the barrels, it looks wet. It could also be caused by modern fuel volatility. As for the hot air valve, it says AC as in Albert Champion, as in the spark plug guy. Part of AC-Delco. The function of it is to direct hot air off the exhaust manifold stove into the carb when it's cold and opens to let in cool air when the engine is hot.


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Last edited:
Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
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Queens, NY
#4
I have to pump it once to the floor to set the choke so it will start
That is correct procedure for a carbureted engine. If the fast idle and choke pull-off are adjusted correctly then it goes to whatever rpm you set it at and stays there until you tap the pedal to drop it down. If it wavers as you state then yes, the pull-off is not right. Getting it right takes some time and requires a cold engine. Rule of thumb is: dies- too lean, stumbles- too rich. It sounds like you have it very close to optimal if it only wavers a bit then settles down. Also know that ambient temperature affects the setting so winter and summer may require a different setting. Look at an older MOTOR manual for the pull-off setting on a engine like yours. Use a drill bit to measure. Ignore the later angle measurement unless you have the tool. Use that as a starting point then adjust as you go. I used to start the car each morning and then adjust it. The next day would tell if it was better or worse.
 
Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
5,515
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113
Queens, NY
#5
As for the hot re-start- are you running the EFE valve? (heat riser) If stuck closed it forces all the exhaust from that side to pass under the carburetor. It will boil the fuel in the bowl. A properly working EFE will open at the temp setting on the Thermal Vacuum Valve mounted on the water crossover on the intake manifold. Make sure the hoses are routed correctly so the EFE hose can vent and open the valve.
 
RegalBegal

RegalBegal

G-Body Guru
Jul 10, 2009
640
416
63
Lebanon, New Hampshire
#6
As for the hot re-start- are you running the EFE valve? (heat riser) If stuck closed it forces all the exhaust from that side to pass under the carburetor. It will boil the fuel in the bowl. A properly working EFE will open at the temp setting on the Thermal Vacuum Valve mounted on the water crossover on the intake manifold. Make sure the hoses are routed correctly so the EFE hose can vent and open the valve.

Speaking of fuel boil, i see he's running an aluminum intake. Are the crossovers blocked? If not, this will also boil the carb.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
23,522
4,238
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Kitchener, Ontario
#7
have you measure the amount the air valve opens on start up?
 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
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Des Moines, Iowa
#8
Speaking of fuel boil, i see he's running an aluminum intake. Are the crossovers blocked? If not, this will also boil the carb.
Its iron. :p
 
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
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113
Des Moines, Iowa
#9
MrSony

MrSony

Comic Book Super Hero
Nov 15, 2014
4,017
1,570
113
Des Moines, Iowa
#10
No heat riser.
 

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