Engine dies at stops

L

Lincoln29

Senior Member
I have two 1930 Model A's and both of them occasionally die at the stops signs. They both have Zenith carbs and I have cleaned and adjusted floats with no changes. I don't seem to have any vacuum leaks. Timing and point adjustments don't seem to matter. The motors run great and idle perfect.
Any other ideas would be appreciated.
thanks,
Jerry
 
You’ll probably get conflicting answers on this. All I know is that I was having the same problem with the float level set to the spec in the manual. I set it about 1/8” lower than that and it hasn’t stalled once since.
 
The Zenith bowl is the problem, the fuel will slosh forward at hard stops. To fix that, when I main stop and go traffic I turn the GAV open about 1/4 turn. No stalling and when I hit the freeway I close it down to about 1/8th open.
 
Good Morning...I run a Model B Zenith Carburetor. It is usually fine. I do have the habit of just advancing the hand throttle a bit as I come up to a stop sign or light. I've had A's off and on since 1963 and its become a habit. Just a note, I've had my 31 Tudor for 19 years...and IT is habit forming. Ernie in Arizona
 
jb-ob said:
Adjust both carbs according to the Owner's Manuals.....no stalling.
Click to expand...

There is at least one important thing not mentioned (as far as I know) in the Owner's Manual.
If you look down the throat of the carburettor, there is a small hole right where the butterfly sits when the throttle is closed. The butterfly should HALF cover that hole. Back off the idle stop and loosen the screws holding the butterfly plate in the shaft. Holding slight pressure on the throttle lever with your thumb in the closed direction, give the plate a tap with the handle of the screwdriver. Keep the pressure on while you tighten the screws. You should not be good but if not, I've been known to either add a little solder or file some of the plate away. Don't go too far.
All of this is assuming the passage behind the hole is clear.
Please report back to the forum when you get it sorted.
 
I had this problem last summer. Rebuilt the carb, checked jet sizes and adjusted the float. It has no longer stalled when stopping.
 
X2 on post #2. (stock Zenith carb) IMHO, Setting the base idle is the first step in correcting the stalls on stop. Setting the base idle is noninvasive and easily done. The Model A Instruction book describes how to o it.
 
On a Zenith carburetor, try turning the idle adjustment screw in (clockwise) 1/4 turn. That will make the idle slightly richer.

On a side note, the Weber carburetor has 3 little holes like what Arnold talked about in Post #7. As the throttle is opened more of the holes come into play. To improve the transition from idle, I drilled out the 2nd and 3rd holes a little bit on my Weber.
 
Thodge said:
You’ll probably get conflicting answers on this. All I know is that I was having the same problem with the float level set to the spec in the manual. I set it about 1/8” lower than that and it hasn’t stalled once since.
Click to expand...

I have had this problem to. Just because you set to factory settings does’t mean that’s what is needed.

As said above, you sometimes have to play with the adjustments to get car running right.

100 years old!

Enjoy.
 
Hello,Had same problem cleaned out carburetor passageways in Zenith’s body , lot of rust particals we’re forced out,reassembled and set to specs, ran fine after that.
 
I had the same problem this summer. The problem after much troubleshooting, the idle jet which should be one solid piece was two pieces. The lower piece of the jet was loose and turning inside the hex part of the jet. I changed the jet and problem went away. I hope this helps
 
My A came with a Model B Zenith carburetor and use to do the same when stopping and I would always have to give it a little gas. I purchased a fuel level setting gauge from Renner's Corner and a float chamber baffle. That really helped and my carburetor does not drip when setting in the garage but I think my biggest improvement was installing a 6:1 high comp head from Snyder's; It idles better, has more power and uses less gas.
 
Synchro909 said:
There is at least one important thing not mentioned (as far as I know) in the Owner's Manual.
If you look down the throat of the carburettor, there is a small hole right where the butterfly sits when the throttle is closed. The butterfly should HALF cover that hole. Back off the idle stop and loosen the screws holding the butterfly plate in the shaft. Holding slight pressure on the throttle lever with your thumb in the closed direction, give the plate a tap with the handle of the screwdriver. Keep the pressure on while you tighten the screws. You should not be good but if not, I've been known to either add a little solder or file some of the plate away. Don't go too far.
All of this is assuming the passage behind the hole is clear.
Please report back to the forum when you get it sorted.
Click to expand...

Interesting, because I have heard of people playing around with things till they hit on the problem. Some I have heard say the idle was just a bit too high, and when they slowed it down (warm engines) everything was fine.
 
Gene F said:
Interesting, because I have heard of people playing around with things till they hit on the problem. Some I have heard say the idle was just a bit too high, and when they slowed it down (warm engines) everything was fine.
Click to expand...

I was told that by "Da Wizard" who is now, unfortunately passed. He took a lot of knowledge with him. That is one thing he left with me via a forum thread.
 
If you can “rev the motor” and take your foot off the throttle does it stall? Or drop to idle and not stall? I had a problem with the motor stalling when coming to a stop but no problem if car was sitting still. I began testing by slowing the car to a stop multiple times. In each case I used a little less brake until I found that I could indeed come to a stop without the motor stalling so long as I was careful with the braking force. I’m not saying that that is a practical way to drive but it was just a test. After thinking it all through for awhile it occurred to me that the most likely problem was a low float level allowing the fuel to slosh fuel forward exposing the rear ports. I raised the float level slightly and the problem went away. This is interesting because 9 out of 10 times the float level in a Zenith is too high. Based on my experience, sometimes you have to just “fiddle” with the various components of the Zenith until you find the “sweet spot”,I have yet to find a Zenith that played by the rules. One could argue that when new they were new at the factory the worked right out of the box, but did they? I think that we make the assumption that all the new Model A’s drove out of the factory just fine. But did they? Based on a friends working “on the line” in Detroit, I would say that there were some that did NOT work fine right off the line. I’m sure that some of the new cars DID have problems and they were sent to an area that was for the exact purpose of correcting whatever the problem was. Keep in mind that there were thousands of new Zenith carbs at the factory so that if there was a problem they just put on a new one. They did not stop the line for anything so if a bolt was cross threaded or any of a million other things occurred they were sent to the repair department. This was what Ford was doing in the 70’s and I have no problem with assuming that they did the same thing in the 20’s.
 
Jeepguy, you ever wonder if when we read these stalling threads if someone has changed the float to the wrong shape and size? I do.

I have a little float scale that even can weigh a float, although I have never used it.
 
You must log in or register to reply here.
Back
Top