So I've got a sb350 with a quadrajet on it with vacuum choke. On cold starts it works perfect, stab the gas once and fires right up. However, once the engine is warm and I shut it down the choke closes. When I go to start it back up the choke stays closed and starts to flood out the engine. I have to get out and manually open the choke while someone else turns the ignition to get the engine to fire. I looked at this thing and scratched my head for quite a while today, and all I can think is maybe there is a spring missing? I pulled the hose off and it is getting plenty of vacuum. I bought this as a reman and it came shrink wrapped to a piece of cardboard.
The choke pulloff is probably bad. When you apply vacuum it opens the choke, it also controls air flap opening.
once the engine starts the choke opens. I pulled the vacuum line off the choke pull off to see what would happen. When I did the choke closed.
The carb mounted choke thermostats can be a pain. Since they are mounted up on the carb they will cool off faster then the engine and close the choke sooner than necessary. I have the same problem with the q-jet in my car. After the engine has been running for a while when I go to restart it I have to leave my foot off the gas and it usually cranks right up. Pumping it even just once will flood it. In the summer time you might adjust the choke to where it doesn't close all the way. It will help the hot starting problem.
is the choke thermostat electric or does it have exhaust tube to heat it? thermostat in the intake on heat riser? all adjust differently > any pics of the carb ?
This link may help: http://www.thecarburetorshop.com/Automaticchokes.htm Make sure the choke is properly adjusted on a cold engine. Jon.
I remember having that problem on a driver and the one man start procedure was to stick a screwdriver in the carb to hold it open a tad. Which, I think the eventual fix was to adjust the choke so it would stay open a tad when hot.
^^What he said--Recommended Reading^^ This will clear up a lot of the mysteries of automatic choke operation. It sounds like you're trying to diagnose a choke problem by just working with the choke pull-off. That's just a part of the equation.
By Vacuum choke I think you mean the Crossover Hot Air heated choke. This requires air to be heated by passing thru a tube heated by exhaust gas. Without this heated air the choke will not open fully.
The electric choke worked well on my OT car with an electronic Qjet. Lasted about 22 years before crapping out, then was replaced during a rebuild and was back to normal.
This electric choke setup is probably the best way to cure what ails you. Just make sure you wire it so it's only "hot" when the ignition is on. Hot air chokes work OK when everything is fresh and new. But you have to have vacuum at the choke housing. And the choke tubes have to be sealed up and have a gasket where the tube goes into the heat well in the intake manifold. And the crossover has to be open and clear from one side of the intake to the other. And you can't use the intake gaskets which block the crossover passages. And you've got have a working heat riser valve in one of your exhaust manifolds. Assuming you even have manifolds instead of headers. But if you keep all that sorted out they work OK. Until they don't.
Well that's the Million Dollar Question for now. So we're all going with the assumption that he's got a hot-air integral choke for now. If he checks back in maybe he'll post some pictures.
Chevys weren't so bad on the cross over but how many of those mopars have you had to clean out I have lost count.
figured out my problem. Its a divorced choke mounted on a edlebrock intake that previously had an edlebrock 4bbl with manual choke. I didn't stop to think that there is suppose to be a heat riser in there. DUH.... For now I'm just going to rig it to stay open, I'm gonna pull the entire motor in a month or two. Thanks all
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