Stalling at stop sign

[Oldengine]

I know this has been discussed before but I still have trouble with the problem. I have often had the stalling issue and just ignore it by opening the throttle a little at a stop. Now a friend has the same trouble so I thought I would run it up the flag pole again. Does anyone have the most likely way to fix this condition??

Thanks, Jim

[nkaminar]

One thing to try is to screw in the idle mixture control screw in 1/4 turn at a time. That will mix in less air and richen up the idle air/flow mixture a bit.

You will get lots of other suggestions.

[Bob Bidonde]

David Renner gave me an education as to why the stalling happens. David's explanation makes fluid mechanic's sense to me. So here it is:
What actually happens when the engine stalls while stopping? When you come to a stop, your carburetor transitions to the idle circuit from the high-speed circuit. The throttle closes but stays open enough so the engine’s vacuum pulls air past it along with gasoline coming out of the idle aperture hole in the throat of the carburetor. When returning to an idle, the air to gasoline mixture is very sensitive because the amount of gasoline being used is very little. If you have the slightest bit of too much air in the mixture from a vacuum leak, the amount of gasoline in the mixture will be insufficient to prevent the engine from stalling. If the idle circuit gasoline supply is restricted or the engine lacks enough vacuum to pull gasoline from the idle circuit, the engine will stall.
The most likely reason is a vacuum leak. However, there other issues affecting the ratio of gasoline to air that will cause stalling including: An undersized or plugged idle jet; An undersized compensator jet starves gasoline flow to into the idle well; The wrong configuration of secondary idle well that causes the well to starve for gasoline.

[old31]

What Bob said is correct.

I would first start by going to: https://rennerscorner.com/carburetor.html

and purchase a B-9599-Z, FUEL LEVEL SETTING GAUGE and start by testing the fuel level.

[chap52]

What Bob said... Nice explanation. Chap

[Fullraceflathead]

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"Bob's your uncle" !!!!!!!!

[alexiskai]

Originally Posted by old31

What Bob said is correct.

I would first start by going to: https://rennerscorner.com/carburetor.html

and purchase a B-9599-Z, FUEL LEVEL SETTING GAUGE and start by testing the fuel level.

Per Dave Renner, "The level of fuel in the float bowl has nothing to do with how the engine runs."

The post Bob is referring to is here:
https://www.fordbarn.com/forum/showp...0&postcount=14

[Big hammer]

Thought my A was dying at a stop going down hill, but with the hood off I could see the fan blades turning very slowly. When I got back home I did some fine tuning of the idle speed and idle mixture……… always do you fine tuning the a thoroughly warmed up engine. The liquid leveling gauges show you exactly what the fuel level is on your car !!!

[old31]

Alex, sorry but I have to disagree. Over the years I have found many stalls at a stop were attributed to the float being way off.

[Gene F]

I have used the clear tube after installation even with the engine running. You definately get an accurate reading then. (idling, and warmed up)

This time of year a bottle of Gumout added to the tank may be in order.

[bobbader]

This issue is coming up a lot lately. I agree with What Bob Bidonde (through Dave Renner) has posted. Old 31 .............. Yes, when float level is WAY OFF, there can be a problem.

The thing is, most folks who post about this suggest that it's a problem that just started happening. Many of them do not suggest they have done anything to make the stalling happen "all of a sudden".

In that case, and especially when warmer weather comes, another thing to check is whether or not the gas cap is venting properly. I'm not saying there is not a carb problem. Just saying that there's another simple thing to check that often gets omitted.

[mcgarrett]

My favorite solution for that problem is a nice Marvel Schebler carb!

[Oldengine]

Hi folks,
Thanks for all the incite regarding toe stalling at stop issue. Much appreciated. It seems that the air mixture going lean is the most likely problem. I made a hit list of about five things to check. I'll run through them and see if I can improve things.

Thanks again,

Jim

[Trapdoor2]

I've been testing...

I have three rebuilt carbs, a Zenith, a Tillotson X and a Marvel Schebler. All three have been run on my Coupe (I don't have any other Model As) and all three exhibit the same stalling behavior to varying degrees. The Zenith is the most sensitive to idle speed. If I adjust her too slow, she'll need a bit of hand-throttle to keep running at a short(er) stop...this behavior is exactly as Mr. Renner describes (and which I agree with).

Neither the Tillotson nor the MS idle smoothly below 470rpm. They smooth out at 500rpm. They won't really stall below 470 but they'll hiccup and stumble. A slight vacuum leak could certainly cause these issues.

All have been float-checked (with the Renner tools) and adjusted as recommended. All have been checked for vacuum leaks, up to the manifold...but not past the carb/manifold interface. No leaks.

I'm convinced I have a slight vacuum leak in the intake manifold/block interface that is the root cause of my minor idle issues. Once I get her back on her feet (the brake drums and backing plates are being boxed for shipment today), I'll pull the manifolds, clean and re-gasket, re-seal, etc.

[OL JENNY]

I fought this problem and all of the carburetor adjustments to no avail. Finally, I replaced my intake manifold with a verified flat surface, new gasket and the problem was solved. My advice is to make sure you check for an intake manifold vacuum leak when troubleshooting your problem.

[Klattu1929]

One of the comments talked about in the forum was the throttle plate relationship to the throat, the idle opening in the throat above the venturi, and idle speed. After eliminating jets, intake leaks, float level, disassembling and reassembling the zenith, I started adjusting my throttle plate, problem lessened, so I installed an old plate from my junk box carb parts. Viola, very rarely will my car die on a down hill stop or at all. Once in a while but rare enough that it's not a problem for me.
If your car just started quitting at a stop then something has changed. Mine was after I rebuilt and installed a swap meet zenith. To bad we don't have a 1930's Ford Mech"s notebook, can't imagine the knowledge about stuff like this we would find.

[CT Jack]

As Dave Renner recommends, check the float level to verify it is set at 5/8". This is the level of the fuel depth in the bowl when measured from the top edge of the bowl to the surface of the fuel. Adjusting the level is not done by trying to bend the float lever. Instead, by varying the thickness of washers under the fuel shut off valve will change the level. Renner and the vendors sell various thickness washer kits. Resetting the float level usually corrects stalling upon stopping.

[katy]

Originally Posted by Klattu1929

I installed an old plate from my junk box carb parts. Viola, very rarely will my car die on a down hill stop or at all. Once in a while but rare enough that it's not a problem for me.

Were there any differences between the 2 throttle plates?

[Klattu1929]

The angle along the edge was slightly different, looked like someone had tried to modify it. The edge wasn't sharp and defined either. The suspect plate had rounded edges. Didn't really pay much attention until the stalling started and had to dig into things. Just another thing to watch out for. I tossed the bad throttle plate so not to mix it with my "good" junk parts. Another plus is my low idle is smoother and doesn't seem to wonder as much.

[gdmn852]

Hello, I was having a similar problem, took carburetor off cleaning it and blowing it out with air ,still had problems, next time around I removed the jets and worked a thin wire into all passages, surprised by how much junk was in them, cleaned jets new gaskets set float and problem solved. Good luck.