1959 hesitation from standing start

[PaulB]

I took out my recently purchased 59 to a car show this past weekend. And i noticed when I'm stopped at a traffic light and i begin to accelerate i experienced a hesitation like its almost going to stall. Then it kind of catches and i start moving forward. Its not a smooth transition from standing start. Any thoughts? Thank you.

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[ADKDave]

I took out my recently purchased 59 to a car show this past weekend. And i noticed when I'm stopped at a traffic light and i begin to accelerate i experienced a hesitation like its almost going to stall. Then it kind of catches and i start moving forward. Its not a smooth transition from standing start. Any thoughts? Thank you.

it sounds like it's choking out. If that's the case, the carb is set too rich.

 

[Ward 57]

I took out my recently purchased 59 to a car show this past weekend. And i noticed when I'm stopped at a traffic light and i begin to accelerate i experienced a hesitation like its almost going to stall. Then it kind of catches and i start moving forward. Its not a smooth transition from standing start. Any thoughts? Thank you.

I would point to your accelerator pump not injecting enough fuel. May be out of adjustment.

 

[willcarterdc]

I’ve had the exact same issue with my ‘57 since the day I got it. Lots of info about it here: http://fordthunderbirdforum.net/***...sitation&sid=229be7c567044dfe5ec0bb8e2c0696d1

I may have a few thoughts and suggestions based on my experience; but first, what carburetor do you have? I’m not at all familiar with the ‘59, so I don’t know how much (if any) of my experience may translate.

 

[74 Harley]

That truly sounds like a n accelerator pump issue. Either it's out of adjustment like @Ward 57 said, or the nozzles are plugged up, possibly the diaphragm has gone bad.

 

[willcarterdc]

An accelerator pump issue is what was suggested in my case as well. That might indeed be the issue; I’m still investigating, but at least in my case, it does not seem to be the cause. I’m not saying that the accelerator pump is not in fact the cause of the original poster’s problem (Or of mine, for that matter; as I said, I’m still investigating. But I have spent many dozens of hours investigating to date, and my problem just doesn’t seem to relate to the accelerator pump. I could ultimately end up being wrong, of course.).

So, I might just say keep an open mind rather than assuming it is in fact the accelerator pump at this point. See, for example, the first couple of sections of this article: https://www.thecarburetorshop.com/Troubleshooting.htm#Acceleratorpumps

 

[74 Harley]

@willcarterdc checking your accelerator pump is a 5 minute job. With the engine off remove air cleaner. Open the choke fully (hold it open) look down the carburetor and open throttle fully.
You should see two steady streams of fuel for the entire throw of the throttle. They should start immediately.
If you don't then you have an accelerator pump problem. It's that easy.

 

[willcarterdc]

Yes

@willcarterdc checking your accelerator pump is a 5 minute job. With the engine off remove air cleaner. Open the choke fully (hold it open) look down the carburetor and open throttle fully.
You should see two steady streams of fuel for the entire throw of the throttle. They should start immediately.
If you don't then you have an accelerator pump problem. It's that easy.

Yep, I did all of that first, thanks. Subsequent investigations were to try to figure out why I was still getting the hesitation/flat spot notwithstanding that I am getting very good fuel flow throughout the entire throw of the throttle. So, I spent a lot of time learning to adjust, and then adjusting, the accelerator pump mechanism in various ways to see if any such adjustments would affect the hesitation and stalling when giving sharp acceleration from a full stop. None of the adjustments have had any effect so far. (I’ve also adjusted various other settings too, of course.)

Anyway: in my case, I’m not too worried about it at the moment because I’ve overcome the issue for now by (1) running the auxiliary fuel pump (2) letting the car warm up more than I typically would before I set off and (3) avoiding giving hard acceleration from a complete stop whenever possible. I’d still like to figure out one day what my underlying issue is; just pointing out my experience that this problem isn’t necessarily/always due to (or solely due to) the accelerator pump. Might be; or it might be something else. Or again, it might be that I don’t know what I’m doing! 🙂 But as you said, I’ve checked all of the straightforward things regarding the accelerator pump in my case.

 

[Ward 57]

The only other thing I can think of is, if your vacuum distributor advance is working properly?

 

[74 Harley]

I'll add to @Ward 57 comment by saying most of these cars are old enough to need the breaker plate in the distributor removed and clean and service the mechanical advance. The springs may need to be replaced also. Minimum of clean and oil.

 

[PaulB]

Great information thank you all. I think the consensus is to start with the carburetor. I know its a four barrel but not sure of the brand. But i will perform the choke test Harley mentioned. Good tip.

 

[willcarterdc]

Great information thank you all. I think the consensus is to start with the carburetor. I know its a four barrel but not sure of the brand. But i will perform the choke test Harley mentioned. Good tip.

Good luck! I’ll be interested to hear your findings.

Forgot to mention: the other thing that helps with this issue on my ‘57 (with original “List 1273-1 carb,” recently fully rebuilt by Holley) is that when I come to a complete stop, I downshift into Low. If I start moving in Low and stay in Low until I get through the point in acceleration where my hesitation/“flat spot” usually manifests before I shift into Drive, that almost always mitigates the hesitation issue. I have to get pretty deep into Low before shifting into Drive in order for this to work, but if I do it right, it works 99% of the time. I haven’t checked what RPM I’m usually at before shifting into Drive - it’s more of a “feel” thing - but I’d say I have the pedal maybe 1/3-1/2 of the way down before shifting into Drive. I don’t have sufficient mechanical knowledge to know why this mitigates the hesitation/flat spot, but it does.

I continue to do this (1) until the car is fully warmed up and (2) even once it’s fully warmed up, i also it if I’m going up a steep hill or I need to go through a busy/tricky intersection. Otherwise, once it’s fully warmed up, I just leave it in drive and drive as normal.