Hi, The old 1969 Buick service manual says you need to adjust the fast idle cam when engine is warm with gear in drive and set rpm to 620. Today with warm engine i turned the fast idle screw to see if it affects rpm but it does not, nothing happens. Shouldn't this be done on a cold engine? Thank you,
I can't say that those instructions make sense to me. What is the procedure for adjusting the curb idle?
I took a closer look today, i saw how it works and i adjusted the fast idle cam. It chokes when engine is cold now with the fast idle cam steps working. Thank you!
I think that the spec for the engine is 1620. It is vital that the procedure be used carefully, as it is possible to get the engine running too fast cold. First, the fast idle setting is on the passenger side of the carb, and may be partially blocked by the linkages. Try the 1620 first, by completely closing the choke blade with the engine warm. Be sure that the fast idle cam rises completely, then start the engine, with the tach connected. Make your adjustment, then evaluate a couple of days, DRIVING the vehicle. This will allow you to determine whether the engine requires a little more or a little less speed when cold. Note that the engine will idle faster warm than cold, and the adjustments will need to be carefully evaluated when the engine is cold. Something to consider before any cold adjustments is the settings warm. Make sure that the timing and advances are working correctly, and be sure that the choke pull-off is properly adjusted, and working correctly. It is very possible for a defective pull-off to choke the engine down to the point of your thinking that the idle needs to be adjusted. Normally, a cold engine requires that the pull-off adjustment opens the choke about 1/8" with the engine running. We'll start there.
Thank you for your reply. I was too fast thinking my choke is okay now. I found out that my thermostatic coil is not making it's way up all the way. I have to help it a little so the choke valve will close. If not it won't start. I have to find out why it's not making it's way all the way up...
These linkages were notorious for sticking due to deposits, and that is how I would proceed. Carefully clean everything with a can of spray carb cleaner, and make sure everything works smoothly, using a carefully calibrated finger. When you are satisfied of everything being clean, try adjusting the linkage to make the choke close completely when the engine is cold. It is verty possible, that due to its age, the spring has lost its tension, and the result of adjusting the closure will result in a choke that will not open all the way. Something to consider is that the crossoever for the intake heat may be blocked, resulting in the choke stove being set open by someone not understanding its operation. You might check for the crossover heating rather quickly after a cold start. Let's go from there.
Thanks again. I used carburator cleaner and now it all moves super. Choke valve closes like it should. What i was asking earlier about setting the fast idle cam with a warm engine...you have to set the fast idle cam on low step and then adjust it to 620 rpm with gear in drive. I don't know how many rpm that gives cold. I prefer to adjust it when it's started cold. Adjust it to like you said 1620 rpm or even a bit less. I don't like 2000 rpm or more on it when cold...
I suspect that, if you set it for 620 on the low step, you will end up with something close to 2200 rpm in park when cold. Something to consider here though is the fact that, with a cold engine, the rpm will be some 200-300 rpm lower than when hot. Now that it works cold, you might simply try several cold starts, and see whether the engine could stand a little less, or a little more idle speed. I suggest making 1/8 turn adjustments, and evaluate for several days. If the carb is properly calibrated for the correct operating conditions, I have found it beneficial to drop the idle slightly. Once the choke is operating correctly, you will be surprised at the tolerance the engine has for even very cold temps. One thing more to consider is the use of the heated air cleaner. This set-up is very adaptable to the climate where you are, and I have found that, if the air is very humid in your area, the engine tends to die at highway speeds without it. Just food for thought.
Ray thanks again! I appreciate it! I don't understand what you mean about the heated air cleaner and with the humid air here in my area and that the engine tends to die at highway speeds?? I have it all set-up stock from factory and it all works inside the air cleaner. Even the exhaust heat riser works great! The engine stays cool even in traffic jam with 30 degrees in summer. Thermo-vacuum switch works good too. But i am curious what you mean exactly....(my english is not 100%). Thank you Ray...
The heated air cleaner performs one function, but the results are two fold. As you know, the heated air cleaner provides heated air from across the exhaust manifold, ultimately heating the incoming air to close to 200 deg. Initially, this performed the function of preventing what was called carburetor icing. This phenomena was the result of the air, as it crossed the venturis, from condensing the moisture in the air. As the fuel, when it entered the air stream, cooled the air through evaporation, it caused a situation called icing. This typically occurred when the temperatures hovered close to freezing, say below 45 deg F. What would happen was that the air, laden with moisure would be cooled by its trip across the venturis, to close to or below freezing. As that moisture condensed across these venturis, the low temperatures would freeze the moisture across them, creating ice, which would prevent the venturis from feeding fuel. When the engine , starved of fuel, would stall, the air flow would stop, and allow engine heat to heat the carb, and the venturis, and thaw the ice. Typically, the driver, attempting to discern the problem, would coast to the side, get out and open the hood. By that time the ice had melted, and when the driver, seeing nothing wrong would attempt to restart the engine, it would fire right up. The heated air would prevent the temps from dropping below freezing soon after the engine started, and thus cured the icing issue. It was soon determined that the warmer air required less choke, which resulted in lower emissions, and it became an emission control. Interestingly enough, it was only the very efficient carbs, like the Qjet, that encountered these issues. My concern, when discussing your choke issues, was that, if the heated air cleaner had been disconnected, the engine would require longer choke engagement, which may have caused either you or a previous owner to "mess" with the choke, causing other problems. You may have noticed that I strongly suggested checking the basics before proceeding. I have seen many chokes "fixed" by those not in the know. Good question, and I hope I answered it for you. I appreciate questions, and there are no stupid ones, only unanswered ones.
Great information and explanation! I understand what you mean. Some people said that you can remove the exhaust crossover pipe to the air cleaner element in the summer...there is no need to remove it in the summer...maybe they do not now how it works! It's cool to see that the warm-up program of the engine works great and to see that it smokes condens on a cold day through the rightside exhaust only. You don't see that anymore on today's cars...not to mention the sound of an old Buick. By the way...after a cold engine is started and runs, should the vacuum diaphragm pull in all the way immediately or does it go in steps and with more time when engine warms-up?
Actually, if the vacuuum is not switched, as with a temp switch, it should pull open as soon as the vacuum is applied. I suspect that your pull-off is getting old, and is only capable of pulling against the choke thermostat as it opens, and loses tension. I would first chek to be sure that the vacuum applied is actually manifold vacuum, (it should be), be sure that there are no controls, as some are operated by air cleaner temp, and check the unit with a pump. There are a couple of caveats here. One is that some of the Buicks, especially the Calif units had two pull-offs, one a primary and one a secondary, operated by a vacuum switch on the air cleaner, which pulled the choke further open as the air cleaner air temp rose to close to 100 deg. The primary is the one having the most effect on cold driveability, and it is the one connected directly to manifold vacuum, through no controls. Make sure that the vacuum port is not blocked, (the other caveat), but I suspect that the pull-off is dying. Also make sure that the vacuum for this pull-off is not connected to other accessories, and if it is, be sure that that accessory is not leaking vacuum. Make sure that the one for that carb is installed, use the number on the carb, and we'll cover the adjustments for it when you have tested yours. If there are any doubts, just replace it, they are cheap, and you do not want the engine to flood cold, which will likely happen on the next very cold day.
Okay, well if i start the car cold now...i have to get out of the car fast to press-in the vacuum diaphragm...because it starts to flood right away. After i press-in the diaphragm it will start running smooth... So yes i need a new vacuum diaphragm...Thank you Ray, enjoy the weekend!
