Cold start issue
Drifting
Joined: Feb 2001
Posts: 1,603
Likes: 0
From: San Francisco, CA
Re: Cold start issue (mg62)
Sounds like you've got it covered mg62. Wow- that is a great picture alright. Someone should hold on to that one for other questions. be glas you have an electric choke. The old spring models (which I think would have been original on your car) are a little more funky - but then thats what makes it a Vette. Have fun. :D
Drifting
Joined: Feb 2001
Posts: 1,603
Likes: 0
From: San Francisco, CA
Re: Cold start issue (R. Bruno)
mg62- if it is still a problem tomorrow it is likely the choke pull-off that is out of adjustment. It is adjusted thus:
1. With car cold and the choke flap closed, put vacuum on that hose we talked about earlier. (Cut it off if you have to and put a new one on when you are done. You can buy it for about 10cents an inch at an auto parts store. Just bring the old one.) Either suck on it or get a vacuum pump (a very useful item to have around a Vette if you are in the mood to spend a couple of bucks.)
2. The pulloff should open the choke flap. Put LIGHT pressure on the flap (opening it a little more) to simulate the air that will be wizzing past there as the engine is running. The opening now in the flap should be 1/4 inch. If it is opening wider, that is your problem. It is getting too much air for a cold engine.
3. To adjust, keep the vacuum on the pull-off (now you are glad you bought that vacuum pump) and adjust the screw you see right there on top. As you do you will see the flap slowly close. Get it to 1/4 inch and it will start right up and stay running until the choke warms and closes.
Let us know how it turns out. :cheers:
1. With car cold and the choke flap closed, put vacuum on that hose we talked about earlier. (Cut it off if you have to and put a new one on when you are done. You can buy it for about 10cents an inch at an auto parts store. Just bring the old one.) Either suck on it or get a vacuum pump (a very useful item to have around a Vette if you are in the mood to spend a couple of bucks.)
2. The pulloff should open the choke flap. Put LIGHT pressure on the flap (opening it a little more) to simulate the air that will be wizzing past there as the engine is running. The opening now in the flap should be 1/4 inch. If it is opening wider, that is your problem. It is getting too much air for a cold engine.
3. To adjust, keep the vacuum on the pull-off (now you are glad you bought that vacuum pump) and adjust the screw you see right there on top. As you do you will see the flap slowly close. Get it to 1/4 inch and it will start right up and stay running until the choke warms and closes.
Let us know how it turns out. :cheers:
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,453
Likes: 2
From: Toronto
Re: Cold start issue (R. Bruno)
Thanks.
When I went out to fire her up today, I found that the half-inch turn of the choke thermostat was probably too much. She was getting too lean a mixture on a cold start, and wouldn't engage.
I took off the air cleaner and I could see that she was sitting cold with the choke flap open a bit, more than an eighth of an inch, maybe a quarter? I hand-tapped the flap closed, and she started up right away. As a result, I loosened the screws on the choke thermostat and dialed it back counterclockwise half the distance that we had dialed it clockwise yesterday. I'll be able to tell on the next cold start whether this worked.
Funny vignette. I was standing out in the front yard this afternoon with my Vette proudly in the driveway, yakking with a neighbour and complimenting him on his new Mercedes vert. He asked me how things were going with the Vette, and I said she's running great and sounding awesome, and "I'm tinkering a bit with the carb". I stopped, and looked at him, and said ... "Now there's a sentence I never thought I'd say ..." Ha!
When I went out to fire her up today, I found that the half-inch turn of the choke thermostat was probably too much. She was getting too lean a mixture on a cold start, and wouldn't engage.
I took off the air cleaner and I could see that she was sitting cold with the choke flap open a bit, more than an eighth of an inch, maybe a quarter? I hand-tapped the flap closed, and she started up right away. As a result, I loosened the screws on the choke thermostat and dialed it back counterclockwise half the distance that we had dialed it clockwise yesterday. I'll be able to tell on the next cold start whether this worked.
Funny vignette. I was standing out in the front yard this afternoon with my Vette proudly in the driveway, yakking with a neighbour and complimenting him on his new Mercedes vert. He asked me how things were going with the Vette, and I said she's running great and sounding awesome, and "I'm tinkering a bit with the carb". I stopped, and looked at him, and said ... "Now there's a sentence I never thought I'd say ..." Ha!
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,453
Likes: 2
From: Toronto
Re: Cold start issue (R. Bruno)
OK, here's the next installment in this saga.
Just went to try another cold start. Took the air cleaner off to take a look beforehand while she's still cold and unstarted just to see what was going on. The choke flap was was wide open. It would not push down manually to a fully closed position. I got behind the wheel and pumped the gas a couple of times (thinking that would set the choke), to no effect. Choke flap still open.
I figured ... hmmm ... the choke thermostat must still have been adjusted too far clockwise. So I loosened the 3 screws and turned it back almost, but not quite, to the original position, which we had marked. Not sure what to do next, while standing over the carb, I manually moved the throttle, and the choke flap snapped shut. I got in the car, and she started up and kept going fine.
Note: I'm not ignoring your three-point plan from a couple of posts up above. As matters stand now, though, it seems to me that the choke pull-off must be working ok, because when the choke flap is down tight enough to give her a rich enough mixture to fire up, the flap does in fact get opened to allow her to continue to run.
What I don't understand is why the choke would not set when I was pumping on the gas earlier. Any chance this last re-adjustment I made will solve the problem?
Just went to try another cold start. Took the air cleaner off to take a look beforehand while she's still cold and unstarted just to see what was going on. The choke flap was was wide open. It would not push down manually to a fully closed position. I got behind the wheel and pumped the gas a couple of times (thinking that would set the choke), to no effect. Choke flap still open.
I figured ... hmmm ... the choke thermostat must still have been adjusted too far clockwise. So I loosened the 3 screws and turned it back almost, but not quite, to the original position, which we had marked. Not sure what to do next, while standing over the carb, I manually moved the throttle, and the choke flap snapped shut. I got in the car, and she started up and kept going fine.
Note: I'm not ignoring your three-point plan from a couple of posts up above. As matters stand now, though, it seems to me that the choke pull-off must be working ok, because when the choke flap is down tight enough to give her a rich enough mixture to fire up, the flap does in fact get opened to allow her to continue to run.
What I don't understand is why the choke would not set when I was pumping on the gas earlier. Any chance this last re-adjustment I made will solve the problem?
Drifting
Joined: Feb 2001
Posts: 1,603
Likes: 0
From: San Francisco, CA
Re: Cold start issue (mg62)
If the car is cold, the choke should shut (set) with just 1 pump on the gas. Then once it starts the pull-off should open it about 1/4 inch to keep it running. If it is not setting, your turning it tighter should do the trick or thr problem is that the linkage was/is binding. It is a long shot but make sure the throttle linkage is not binding in anyway and that it is clean and free of muck. Let us know how iot turns out. :cheers:
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,453
Likes: 2
From: Toronto
Re: Cold start issue (R. Bruno)
Here's the latest wrinkle.
Went to do my cold start, and she started up fine, and kept running fine, for several minutes (with me applying light pressure on the gas pedal to keep her revving above 1000). At some point after least two and probably three minutes from ignition, I took my foot off the gas to let her idle on her own, and when she started to falter I put some pressure on the gas, but the idle kept dropping, like she wasn't getting any gas, and then she stalled.
Now, she won't start. Like she's flooded. Dang.
:mad
Went to do my cold start, and she started up fine, and kept running fine, for several minutes (with me applying light pressure on the gas pedal to keep her revving above 1000). At some point after least two and probably three minutes from ignition, I took my foot off the gas to let her idle on her own, and when she started to falter I put some pressure on the gas, but the idle kept dropping, like she wasn't getting any gas, and then she stalled.
Now, she won't start. Like she's flooded. Dang.
:mad
Drifting
Joined: Feb 2001
Posts: 1,603
Likes: 0
From: San Francisco, CA
Re: Cold start issue (mg62)
This is deja vu all over again. But really, it sounds like the pull-off is not working correctly. If it is opening too much it will do as you described because it is getting too much air to keep running, which is why keeping your foot on the pedal helps. Check to see that it is opening about 1/4 inch when you put vaccuum on it. If the pull-off is opening correctly as per the earlier comments then adjust that fast idle screw. It is located near the choke linkage down really low. It is hard to see at first. You may have to hunt around or remove the 2 screws holding the pull-off any just move it out of the way and you will see it. Turn it clockwise a turn or so to raise the fast idle and see what you get.
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Drifting
Joined: Feb 2001
Posts: 1,603
Likes: 0
From: San Francisco, CA
Re: Cold start issue (mg62)
This is deja vu all over again. But really, it sounds like the pull-off is not working correctly. If it is opening too much it will do as you described because it is getting too much air to keep running, which is why keeping your foot on the pedal helps. Check to see that it is opening about 1/4 inch when you put vaccuum on it. If the pull-off is opening correctly as per the earlier comments then adjust that fast idle screw. It is located near the choke linkage down really low. It is hard to see at first. You may have to hunt around or remove the 2 screws holding the pull-off any just move it out of the way and you will see it. Turn it clockwise a turn or so to raise the fast idle and see what you get. Is the car idling ok when it is warm?
Thread Starter
Drifting
Joined: Jan 2002
Posts: 1,453
Likes: 2
From: Toronto
Re: Cold start issue (R. Bruno)
Went to start it again. After some hard cranking (I'm probably doing permanent damage to the starter), she started and ran for several minutes. She was just about fully warmed up, and idling fine on her own. I got out, put the air cleaner back on, closed the hood, got in, gave it a short sharp rev ... and she bogged down and died.
Battery's drained again. Trickle charging ... again.
What I don't understand is what this could have to do with either the pull-off (because it started initially and stayed running) or the fast idle screw (because I was holding the idle up myself with pressure on the pedal). It seems vulnerable to this problem any time up until being fully warmed up.
Battery's drained again. Trickle charging ... again.
What I don't understand is what this could have to do with either the pull-off (because it started initially and stayed running) or the fast idle screw (because I was holding the idle up myself with pressure on the pedal). It seems vulnerable to this problem any time up until being fully warmed up.
Pro
Joined: Jun 2001
Posts: 672
Likes: 0
From: Quebec
Re: Cold start issue (mg62)
Make sure you didn't got the choke linkage stuck. Do you have the stock air cleaner on there?
Something is not right, your carb is in problem. There's an adjustement somewhere that is off. Do you have Lars paper on Quadrajet? It could help you understand how it's working. The thing is that not much mecanics fully understand these carb. Even if you go to a garage, they'll get it all wrong. Maybe you could try turning your choke assembly again. Hard to tell. Good luck.
Stephan
[Modified by American Boy, 12:06 AM 5/9/2002]
Something is not right, your carb is in problem. There's an adjustement somewhere that is off. Do you have Lars paper on Quadrajet? It could help you understand how it's working. The thing is that not much mecanics fully understand these carb. Even if you go to a garage, they'll get it all wrong. Maybe you could try turning your choke assembly again. Hard to tell. Good luck.
Stephan
[Modified by American Boy, 12:06 AM 5/9/2002]
