Stalling Out

I just changed my Thermostat from Stant 195 degree to Stant 180 degree #45358. This change helped with my hot start issues a lot, but when I go to start the car cold it stalls out.

I have the thermostatic air cleaner hooked up, but I don't think it works at all.

When starting my car COLD, I pump the gas once, about midway to the floor, turn the engine over, it fires up, and then stalls out. I start the car again, this time pumping the gas to keep it alive so it wont stall out. Once my car warms up a little bit, it idles fine in park.

When I put my car in reverse to back out, it runs a little and then stalls out.

My 198 idles fine in park and neutral. But in Reverse and Drive from a COLD start, it can barely stay alive.

My idle is set at about 850 rpm in park and neutral. In reverse and drive, it is very low, how can I adjust idle when my car is in gear? Also, how can I go back to having my car pumped once and having the car able to not stall, when starting cold.

I know my Car runs way too lean, I know where the idle mixture screw is on my holley 1920, but which way do I turn it to richen the mixture and how much?

Thanks

Haha, loving the 1920 yet?

Sounds like the choke is non-operational. That's the piece on the manifold behind the carb, with a long rod extending from it to the carb.

When the engine is cold, there's a spring in that choke unit that winds tighter because it's metal and that's what metal does according to temperature changes. When it winds tighter, it pulls that rod toward the choke unit. That in turn pulls the choke plate closed at the top of the carb and if everything is there and accounted for, also moves the fast idle cam on the carb so that the engine idle speed is increased until the choke disengages.

The choke disengages when the exhaust manifold it is mounted in warms that metal spring up enough so that it unwinds(remember the way metal acts) and PUSHES that rod out. That reverses the entire operation I described earlier.

It's a VERY simple operation. Those don't even have the electric assist yet. The choke rod has to actually be connected to the carb, it has to have tension on it. If it doesn't, the choke spring might be broken.

Google slant six choke and you'll find plenty of pictures of that thing.

Also, on the side of the carb, the firewall side, you'll see two screws that look like they adjust the idle. They do. The one closest to the CENTER of the carb adjusts the base idle. Look at the other end from where you put the screwdriver tip and you'll see that it hits the carb itself. Base idle is the idle speed warmed up, NO CHOKE ON.

The other screw slightly to the REAR of the car adjusts the fast idle. It rests on a little metal step looking deal, and that controls how fast the engine runs when the choke is engaged. The choke has to WORK for THAT to work.

On the idle mixture:

Do this with the car warmed up fully. Find the mixture screw on the passenger side of the carb at the bottom. There's only one. Take the screwdriver and slowly turn it one direction. If the engine starts to slow down, stop, go back the other way. if it speeds up the more you turn, turn it until you hear the engine start to slow again and STOP.

Your GOAL is to finesse that mixture screw back and forth until you have the engine idling as fast as possible. It'll slow down when you turn too far left, and it'll slow when you go too far right. Right is lean, left is rich.

After this you should be an expert on Slant six chokes and slant six mixture adjustment. You adjust ALL carbs the same way. Back and forth with the mixture screw or screws until the engine idles fastest.

Here is my own '73 doing it's winter smoking thing. This is how it is supposed to start even during the dead cold. This was with it's original 1920 carb.

[ame="https://www.youtube.com/watch?v=YfT4yAJuvfI"]New Year's Day Slant Six smokathon - YouTube[/ame]

I did as recommended. I found out to get the car running really good on the first try, all I have to do is pump the gas really lightly so the choke clicks shut, then I turn the key and vroom! the engine idles at high rpm and then kicks down pretty low. When I put it in reverse the engine idles a bit and dies. This is all from a COLD start. HOT start the engine idles fine very low rpms, with no problem with idle in reverse.

Idle in reverse or drive, from a cold start, and the car stalls out. Drive the car a little bit and get the engine going and im fine.

I hear a squeaking noise from under the hood. I just replaced the intake manifold, and rubber valve cover gasket. The PCV valve can be manipulated easily, as well as the breather element, both are able to wobble around, and the PCV grommet has a little oil on it. Could these be a vacuum leak and the source of a squeak/bad idle?

Thanks.

Pull the choke spring assembly out of the choke well on the intake manifold and see if it has a nut on the side and some markings on the side of a small plate on the spring that has scale markings with L and R at opposite ends of the scale. Loosen the nut and adjust it towards R (rich) a step and re-try cold start-up. This will keep choke engaged longer and more and help your cold-idle-in-gear issues. You may need to re-adjust the idle speed screws too after this.

You may have a to re-adjust this in the late fall and in the spring. (Fall and spring tune-ups was a common practice in this vintage of cars.)

Carbureted engines need some warmup time so the choke opens all the way, or it'll load up and die from WAY too much fuel till the choke opens all the way.
This could be verified if you see black smoke when you start it back up again.

I say this because you found out that a carbureted engine needs to have the choke set before starting, so I figured you must have only owned fuel injected cars before this.

In any case your issue's all sound like carb idle mixture and choke adjustments.

Also, I would check all the timing systems.

look down the carb and see if a 1/16" drillbit will fit thru the hole closest to the head (not the accel pump hole that "boss" above it)

I fixed the issue! I removed the hoses that were connected to my Thermostatic Air Cleaner and the hose that connected to the carburetor. I put a rubber fitting over the vacuum port on the carburetor. The car is now able to remain idling in Reverse and Drive.

I believe there was a vacuum leak from somewhere, or one of the components to the air cleaner was bad, thus creating a vacuum leak.

I inspected the choke and it was now fully open when idling, now I can adjust the mixture and idle speed properly without vacuum leaks.

1970Dart198 said:

I fixed the issue! I removed the hoses that were connected to my Thermostatic Air Cleaner and the hose that connected to the carburetor. I put a rubber fitting over the vacuum port on the carburetor. The car is now able to remain idling in Reverse and Drive.

I believe there was a vacuum leak from somewhere, or one of the components to the air cleaner was bad, thus creating a vacuum leak.

I inspected the choke and it was now fully open when idling, now I can adjust the mixture and idle speed properly without vacuum leaks.

Click to expand...

There ya go.
SWEET!

Great. Sounded like a vacuum leak, though Holley 1920's often idle lean if the internal metering block gets plugged. Also, check that the "choke pull-off diaphragm" at the top of the carb works. That is critical in getting easy cold starts. The choke should be closed fairly tight when cold and the pull-off should pop it open slightly the second the engine fires. If not, it will run rich and die. Check that the diaphragm holds vacuum.