When I start my 61 cold, the fast idle takes it to about 2000rpm's. After a period of time it steps down to about 1700rpm's. Then a strange thing happens. Instead of kicking down further as the temperature comes up, the rprm's go up to around 2200. If I try and rush the process by taking it off the fast idle,it won't run until warm. This occurs every start from cold. Is this an electric choke problem? After the car is warm and idling normally it runs fine.
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Re: C1-61 Fuel Injection
What you describe may not be too abnormal, other than you have the fast idle RPM set a lot higher than I have mine. After a cold start, my car will begin to idle a little faster as it begins to warm up if I leave it on the fast idle cam. My fast idle is set to about 1500 RPM. I have a 62 FI which has a different choke setup than the 61, but I have ben tinkering with a friend's 61 lately and it does sort of the same thing. John DeGregory told me recently that the older FI's with the cold enrichment circuitry make take as much as 5 min. to get off the cold enrichment system entirely. -
Re: C1-61 Fuel Injection
Thanks Ed. I had spoken with John about two months ago and I thought he had told me the same thing. I think I will check the fast idle setting. It just bothers me to see such a high idle on a stone cold engine for such a long period of time. If you take yours off the fast idle cam prematurely will it run or does it stall?Comment
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'57 - '61 FI choke functions
The early FI electric choke design performs three functions: it boosts the venturi vacuum signal to the main diaphragm (with partial intake vacuum), it shuts off vacuum to the enrichment diaphragm, and it positions the fast idle cam.
The fast idle cam is gradually moved out of the way as the choke internal mechanism heats up and rotates. This internal rotation also stops the other two choke functions, but in distinct steps.
The sudden increase in idle speed that you're noticing during the warm-up period is normal. This happens when intake vacuum is first sent to the enrichment diaphragm. This causes the enrichment lever to suddenly swing from the rich stop to the lean stop. By the time this occurs, the engine is good and ready for a leaner mixture.
As the young people would say, the '57 - '61 FI choke design "sucks". The stepped release of two choke functions ensures that there will be periods during choke operation when the mixture will be too rich. You can cure it by setting the choke too lean, but that introduces it's own problems.
In my opinion, GM never did get the choke design right on the FI engines. The '62 choke was the closest to perfection. The electric heat doesn't cause as many hang-ups as the exhaust manifold heat in the '63-5 models.Comment
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Re: C1-61 Fuel Injection
I usually don't let my car idle very long on fast idle. I have the choke set very lean, also. Keep in mind that I live in the deep South, so real "cold" weather isn't usually an issue. When it first starts, it will idle at around 1000-1100, and in a minuet or so increase to around 14-1500, which is where I have it set. Once started, it usually doesn't die, even at low RPM.Comment
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Re: '57 - '61 FI choke functions
after reading this thread, maybe I can give some data points and get help myself too. I have an original 61 fuelie big brake and it starts fine and runs up to 1700 max and come down nicely over 3 minutes. It is perfect and confirms these cars can run perfect. Some guy in california (bay area) did this car before I bought it. A genious.
As far as letting a cold engine started and then going to high idle, I recommend using the starter as a prelube and use synthetic oil. I never help my car get started, I just let it turn till oils on top, then I kick the idle cam to get it going. To each his own, but a car thats starts right away is not a good thing.
My problem is my 60 big brake fuelie. I has a podel rebuilt unit that fired up ok for a while, ran rich as hell, and now it crapped out. It was rebuilt by Podell (beautiful show piece job) it never ran 'right', put 100 miles on it. I ran it out of fuel once (just trying to get it running and did not pay attention to the gauge) and then got it back running again. If anyone has a recommended rebuilder in the midwest, please let me know (podel wanted nothing to do with my problem, except if I pay for another rebuild). bcward@direcway.comComment
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Re: '57 - '61 FI choke functions
Jerry, what should be a normal progression of rpm as the car warms up and comes off of high idle? What should be the time frame to a normal idle assuming a reasonable outside temp?Comment
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Re: '57 - '61 FI choke functions
Call Jerry Bramlett. His number is in the user profiles. He will do a repair/calibration on FI units and has a pretty quick turn around.Comment
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Short and longer versions
Short answer: The high fast idle speed setting (according to GM) was 1,800 rpm in 1961. Typically I set it to come off after 4-5 minutes in cold weather.
Longer answer: The time you WANT the choke to maintain a fast idle will vary with the ambient temperature, how quickly your car warms up, and how you drive. On a '61 FI, the fast idle will stay on just as long as it takes the electrically heated choke coil to rotate the internal mechanism. The 1961 FI choke design isn't influenced by the engine's air intake volume. That's why it's such a weak sister to the '62 - '65 flapper type chokes.Comment
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Re: '57 - '61 FI choke functions
send it to De Gregory. mikeComment
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Re: '57 - '61 FI choke functions
Call and send it to De Gregory.....he's Great. He has always been very helpfull with my 60'. Every time, anytime.Comment
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Re: '57 - '61 FI choke functions
John does super restoration work. As a result, he has a backlog of work covering several months. Jerry can fit the repair/calibration jobs in pretty quickly in most cases.Comment
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