Re: Anybody got the end all cure for vapor locking?

Posted by DavidM On 2022/1/11 16:42:26
The car in question (1929 Packard) has a vented float bowl so boiling fuel in the carburetor may not pressurize the bowl. The vent is a small hole in a screwed cap, I removed the cap on my cars providing a bigger vent opening, that made no difference
In my opinion the problem is simply that the fuel drawn into the engine is a mixture of liquid and vapor. The vapor has negligible energy so the car starts "bucking", as the vapor part starves the engine of fuel. Pulling out the choke or full throttle can provide slight improvement but once it starts, stopping and cooling the vacuum tank and carburetor with a wet rag will provide temporary relief.
The problem is as simple as that, the cure however is far from simple, how to keep the fuel cool.
It's worth adding that on later model cars vapor lock might be due to the fuel pump not delivering vaporized fuel, pumps deliver liquid not vapor. On cars with a vacuum tank, its not a pump, its simply a tank under negative pressure (when the float drops) and as such will suck liquid or vapor if required.
A final comment despite this being a real PITA when it happens, sometimes a year or two will pass without a vapor lock incident occurring leading to the belief that the latest "fix" has somehow been the cure, then when conditions are "right" it happens again

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