Rough cold starts, but then runs perfectly

[Mister-B]

I've got a '69 C20 that has a rebuilt 350 V8. It runs and idles perfectly, but it is a little hard to start the colder it is. I have to pump the gas a bit while I crank it, and have to rev it while it warms up. Sometimes it dies if I don't rev it enough while it warms up. But then it runs perfectly. It idles and accelerates great and I wouldn't change a thing.

Do I just need to work on my technique to start it, or is there something I need to adjust or fix?
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[67swb72klb]

sounds like the choke is not closing all the way in the cold

[Mister-B]

Originally Posted by 67swb72klb

sounds like the choke is not closing all the way in the cold

Do you mind giving me some details on how I might fix that?
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[trac209]

little more info please. what carb are you running? electric choke?

[truckster]

Originally Posted by 67swb72klb

sounds like the choke is not closing all the way in the cold

I agree. If you're not sure what the carb is, post a picture and we can help you out.

[Mister-B]

Originally Posted by trac209

little more info please. what carb are you running? electric choke?

Not sure, but here are some pics I just took, if you wouldn't mind shedding some light on it.







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[truckster]

That's a later-model Quadrajet with an electric choke.

With the air cleaner removed and the engine cold, open the throttle by hand. The choke plate (the one over the primaries in front) should close. If it's not closing, the choke may be set wrong. I don't have the specifications with me right now, but there are three screws on the choke housing (which tells you the carb has been rebuilt at some point, because they were originally rivets) that you can loosen slightly. Turn the black part of the choke to the right (clockwise) to increase spring tension on the choke. It should close firmly but not be really tight.

[Mister-B]

Originally Posted by truckster

That's a later-model Quadrajet with an electric choke.

With the air cleaner removed and the engine cold, open the throttle by hand. The choke plate (the one over the primaries in front) should close. If it's not closing, the choke may be set wrong. I don't have the specifications with me right now, but there are three screws on the choke housing (which tells you the carb has been rebuilt at some point, because they were originally rivets) that you can loosen slightly. Turn the black part of the choke to the right (clockwise) to increase spring tension on the choke. It should close firmly but not be really tight.

Thanks! Ok, now go easy on me here because its been a while since I worked on an old engine. Please tell me the best way to manually open the throttle?

Any other specs you can look up and add would be really helpful. Thanks
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[trac209]

I can tell right now from the pics your choke is set too lean when cold. As a baseline setting the notch directly across from the wire on the choke housing should be set to the centre of those little notches. In other words turn clockwise roughly 1/5 of a turn.
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[MacGyver72]

I thought you would want to turn the choke housing to the left to close the butterfly valve. When properly adjusted, it should have a small gap to allow a small amount of air. In the photos it's completely open so unless it was a warm motor when you took the photos or if the throttle had not yet been pushed after shutting it off, this is definitely the problem.

[Mister-B]

Originally Posted by trac209

I can tell right now from the pics your choke is set too lean when cold. As a baseline setting the notch directly across from the wire on the choke housing should be set to the centre of those little notches. In other words turn clockwise roughly 1/5 of a turn.
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Thanks! This is second nature to you, but for me... Not so much. Could you please help me see what you're looking at? I want to adjust it, but I don't know where
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[Mister-B]

Originally Posted by MacGyver72

I thought you would want to turn the choke housing to the left to close the butterfly valve. When properly adjusted, it should have a small gap to allow a small amount of air. In the photos it's completely open so unless it was a warm motor when you took the photos or if the throttle had not yet been pushed after shutting it off, this is definitely the problem.

The truck had been sitting about 2 hours, and it's a cold day. Does that change anything?
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[trac209]

Ok the aluminum housing on the left side of carb with the black plastic face and red wire going to it is your choke adjustment. With the engine cold go hit the gas pedal to set the choke. Then loosen the 3 screws and turn the black face counter clockwise until the choke just closes at the primaries. You'll see the plate move as you do that.
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[MacGyver72]

Agreed. Turn it COUNTER clockwise until you get the desired closure.

[MacGyver72]

OH and do this without it running. Hit the gas as trac209 says and follow his instructions.

[Mister-B]

Originally Posted by trac209

Ok the aluminum housing on the left side of carb with the black plastic face and red wire going to it is your choke adjustment. With the engine cold go hit the gas pedal to set the choke. Then loosen the 3 screws and turn the black face counter clockwise until the choke just closes at the primaries. You'll see the plate move as you do that.
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Thank you. Is this it?


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[Mister-B]

Originally Posted by MacGyver72

Agreed. Turn it COUNTER clockwise until you get the desired closure.

Thanks man
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[trac209]

Yes that's it
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[MacGyver72]

yes. Losen the three screws after you hit the gas pedal and turn it. Watch the butterfly valve on the carb close to "slightly open". tighten your screws and start it up. See what happens.

[Mister-B]

Originally Posted by trac209

Yes that's it
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Also, where you say it will close at the primaries, is that the gold flaps at the top of the carb?
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[MacGyver72]

yes. I've been calling it the butterfly valve.

[MacGyver72]

By the way. It's gold because of gum and varnish. Clean your carb with carb cleaner and that will improve performance too.

[Mister-B]

Originally Posted by MacGyver72

yes. I've been calling it the butterfly valve.

Ok, I just did it, but I can't see those flaps at the top of the carb move. What I DO see, is a metal deal to the right of the choke adjustment that moves up or down as I rotate the adjustment counterclockwise or clockwise. So, I ended up turning it counter until it moved, and I stopped. I started it, and it fired right up, but I don't know of that's because I pumped the gas in the first step. It sure seems better to me though, so I'm hoping this did it.

Thanks guys!
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[MacGyver72]

It could be that the choke isn't connected. Move the butterfly valve by hand and see if you feel resistance either way. There is a small rod that goes down through the carb to the choke and it can be a pain to connect when rebuilding one. If the butterfly valve moves really easily and you feel no spring resistance either way, it isn't connected.

[Mister-B]

Originally Posted by MacGyver72

It could be that the choke isn't connected. Move the butterfly valve by hand and see if you feel resistance either way. There is a small rod that goes down through the carb to the choke and it can be a pain to connect when rebuilding one. If the butterfly valve moves really easily and you feel no spring resistance either way, it isn't connected.

Is this the butterfly valve?



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