1959 Hesitation from a standing start

[PaulB]

I rebuilt the carburetor, checked the engine compression, checked the vacuum and timing, and everything is good. I also replaced the points and spark plugs. Before i did all this i had a hesitation from a standing start like it wanted to stall. But after doing all this i still have the hesitation. I should add it starts great, idles great and runs great on the road. So I'm stumped. I bought this car about 4 months ago and have driven it to 3 car shows, probably less than 100 miles. When i got the car it had a full tank of gas and obviously, I have not used much of it. So my question is and i know I'm reaching but could it be bad gas? I have no idea what kind of gas the car was filled with or how long it was in the tank. I'm suspecting it might have been regular instead of the required premium. It's the only thing left that i can think of that might cause the hesitation. Also is there some gas booster or additive i could put into the tank to address this? Love to hear your thoughts.

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[knuckle47]

Off the top of my head, have you checked the timing? Did the re-build include a new accelerator pump in the carb?

 

[sre]

I am having the same issue, my car is a '57 w/312 4V. After checking everything I could think of I found a problem with the vacuum advance and the gasket between the advance and the fitting. If you have a vacuum pump check the advance to see if it works see if it will hold vacuum. I have checked 5 different ones,some hold vacuum till you take the pump off, some leak down fast and some leak down slow. I don't know what is needed to maintain good operation. I have corrected my problem 96%.

 

[Hernando Muñoz]

I agree timing and the quality of the accelerator squirt (from the diaphragm pump in the carburetor) are critical. Nevertheless, these cars don't run well with the new "alcohol +gasoline" that is sold nowadays, so you may have to further adjust the timing (probably advance a couple of degrees to cope with the alcohol) and be sure your carburetor components will survive the alcohol...

 

[74 Harley]

I would look into the accelerator pump. Does it start to squirt right away? Do both sides have equal strong squirts?

 

[Hernando Muñoz]

I would look into the accelerator pump. Does it start to squirt right away? Do both sides have equal strong squirts?

Depending on the carburetor arrangement, they should squirt (as soon as you move the accelerator linkages to test it) in one set of barrels (the "low speed"). But the timing advance is critical too. Check your engine specs, and if the timing chain is old (like mine), you may need to move the distributor to advance 2 or 3 degrees more (BTDC).

 

[philipehlinger]

I rebuilt the carburetor, checked the engine compression, checked the vacuum and timing, and everything is good. I also replaced the points and spark plugs. Before i did all this i had a hesitation from a standing start like it wanted to stall. But after doing all this i still have the hesitation. I should add it starts great, idles great and runs great on the road. So I'm stumped. I bought this car about 4 months ago and have driven it to 3 car shows, probably less than 100 miles. When i got the car it had a full tank of gas and obviously, I have not used much of it. So my question is and i know I'm reaching but could it be bad gas? I have no idea what kind of gas the car was filled with or how long it was in the tank. I'm suspecting it might have been regular instead of the required premium. It's the only thing left that i can think of that might cause the hesitation. Also is there some gas booster or additive i could put into the tank to address this? Love to hear your thoughts.

Suggest checking gas cap is venting properly and engine running is not creating a vacuum in the tank. Also, air cleaner....take if off & see what happens. Otherwise other comments good ones, but sometimes it's the simple things. Had a similar issue with my 55. Also, use ethanol free gas if you can find it. Ethanol is an alcohol which absorbs water, particularly when it sits. Put in some dry gas, run it & refuel with ethanol free.

 

[willcarterdc]

I’ve been having the same issue with my ‘57. I had the carb fully professionally rebuilt by Holley; adjusted the accelerator pump; have a vented gas cap; and use only ethanol-free gas. Still have the issue. So, I’ll be following this with interest!

In my case, three things tend to help. The hesitation on acceleration from a complete stop still happens, but I can now avoid a stall 99% of the time if I (1) have the electric fuel pump running; (2) start in Low gear and then shift to Drive once I get past the “flat spot”/point of hesitation; and (3) let the car warm up before I start driving. I’m not sure what it indicates that these techniques ameliorate the problem; they just do. But I’d like to actually fix it eventually.

 

[knuckle47]

I have had some old gas in cars that were not used much and if you feel a strong suspicion that it’s the fuel, siphon it out and use it a the lawn mower if you have one. Refill with fresh fuel… here in the GARDEN STATE, I have yet to see non ethanol gasoline on the routes I travel. I have used pump fuel in everything from 1920’s motorcycles to 2021 cars and a lot in between. Never had a problem

 

[PaulB]

All great tips and suggestions. Thank you. Fortunately I have access to non-ethanol gasoline here and that is what run all my cars on. I like the idea of advancing the timing a couple of degrees however. Right now its to spec at 6 degrees BTDC. And there seems to be adequate squirt from the accelerator pump on the carb. And the vacuum is holding fine and I'll check to see if my gas cap is vented. I did have the carb professionally rebuilt. It's a Carter 4 barrel. I'll take it out this weekend. Maybe it just needs to warm up some.

 

[cokefirst]

If this only happens when the car is cold, then it could be choke adjustment etc. If it happens all the time, then it is most likely the accelerator pump. Adjusting all the things on a 65 year old carburetor is tricky.

 

[66bluebird]

If this only happens when the car is cold, then it could be choke adjustment etc. If it happens all the time, then it is most likely the accelerator pump. Adjusting all the things on a 65 year old carburetor is tricky.

I had this with my '66. Turns out the "mechanic" who installed my Petronix did not have it hooked up to a 12 volt source. After I installed the recommended relay to get the full 12 volts to the Petronix all was good. Sad thing is mechanic said he has installed a bunch of them that way!!!!!????
If you have points then this is not the issue.

 

[willcarterdc]

To follow up, for folks searching for this issue in future:

In my case, this issue on my ‘57 T-Bird was because the float was set too low. Raised the float level (well, has a mechanic do it) and the problem immediately and permanently went away.

I can’t say that the float level is the only thing that can cause this problem; indeed, I’m sure that there are many other things that can cause this symptom. But I wish I would’ve checked my float levels first; would’ve saved me many months of time and aggravation.